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TECH TIPS
also see upkeep and
performance hints on our message board at
board.mgclub.org
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| AMGBA Technical Sections (Volume I) - copy of all technical topics published by the AMGBA 1975-1987, over 300 pages, indexed: (contents here: $30 plus S & H | |
| AMGBA Technical Sections (Volume II) - copy of all technical topics published by the AMGBA 1988-1996, over 300 pages, indexed (contents here:: $30 plus S & H | |
| AMGBA Technical Sections (Volume III) - copy of all tech topics published by the AMGBA 1997-2007, over 300 pages, indexed (contents here): $30 plus S & H | |
| AMGBA Technical Sections (Volume IV) - copy of all tech topics published by the AMGBA 2008-2017, over 300 pages, indexed (contents here): $20 plus S & H | |
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Technical tips, advice and shared Information.........That's what this page is all about. This is only a very small part of the tips that appear in each issue of the member magazine.
There are also more tech tips and member recommended repair shops in the Members Only area and our TECHNICAL STAFF is prepared to answer your technical questions. See contact information in the Members Only area. Immediate help can also be obtained by posing in our Facebook group at www.facebook.com/groups/americanmgbassociation.
A complete copy of all the Technical Sections, topics, questions and answers published in the OCTAGON is available. Volume I contains reprints of the OCTAGONs published from 1975 to 1987. Volume II contains reprints of the OCTAGONs published from 1988 to 1996. Volume III contains reprints of the OCTAGONs published from 1997 to 2007. Volumes I & II & III each sell for $30 each plus $5 S&H
($20 each emailed). Volume IV contains reprints of the OCTAGONs published from 2008 to 2017 and is available for $20 plus $5 S&H ($15 emailed). Volume III and IV together on a CD-ROM in a pdf file and is available for $20 plus $5 S&H ($20 emailed). Combos of the above are also available at the club store.OCTAGON ADVERTISERS (including Insurance, Parts, Service)
MG Photo Based Color Code Guide
(newest articles first)
Survival Tools
Transmission Not
Engaging
MGB Engine Replacement
Tachometer Problems
Clutch Slave Cylinder
MGB Center Console
Drain and Flush Cooling System
Starting Problems
Clutch Problems
Timing Adjustments
Top Installation
Oil Pressure
Emissions and Timing
Stiff Steering
Carburetors
Replacement
Tires
Bleeding Brakes
Wire Wheel
Conversion
Gear Oils
PC Equipment
Clutch Burning and Slippage
Winter Car Wash
No Electrics
Intake Grille Replacement
Pulsating Brakes
Starting Problems
Brakes
Floor Pan
Replacement
Broken Antenna Replacement
Setting the Vacuum Advance
Drain Plug Oil Drip
Rear End Noise
Wiper Motor Removal
Electrical Connections
Battery Cut-Off Switch
Low Oil Pressure
MG Tire Sizes
Clutch Freeze
Correct Engine Oil and Low Oil Pressure
Backfire on Deceleration
Front Brakes
Top Tips
Car Not Starting
Replacement Tire Info
Battery Replacement
Overdrive Repair
Brake Drums
Lucas Generators
Restoration -
Painting your MG
Tire Rotation -When and Why
Wire Wheel Inspection
Oil Filters
Mysteries of Motor Oils
Squeaky Brakes
MGB Suspension Rebuild
Battery Drainage
Problems
On the Subject
of Oil Pressure
Carpet Kit Installation
Weak Spark
Please note: Questions and answers are provided for information and advice purposes. No liability either express or implies is assumed by reliance on the information presented either by the writers or the AMGBA. Some or all of the below is from our message board at board.mgclub.org.
Also be sure to see our message board at http://board.mgclub.org on our website for immediate help from your fellow members.
Wiper Motor Removal
Art Isaacs
Q: I need to replace the wiper motor in my Mark I MGB. What is the best way to do this?
John
A: The best, but most involved way to get to the wiper motor is to remove the instrument panel. You should be able to get at the drive unit by removing the glove box and cover (door), but it is a contortionist’s job and, if the drive cable is frozen as well (or, probably more likely, the real cause of it not working in the first place), it becomes even more difficult to tackle with all the instruments and ducts in place. I’d still try it first, if just to disconnect the drive cable to see if the motor is actually frozen.
I have an article about how to remove the dash on early MGB’s and the pictures clearly show the motor location and difficulty of access. Please see it in the Upkeep and Performance Hints area of the May 2008 issue of the Octagon.
Replacement wiper motors/drive unit (though without the drive gear) are available at a price. Moss offers the unit less the gear for about $460 (Spring/Summer 2007 catalog, p/n 145-510). Be sure to recheck the price on-line before ordering. The gear is not offered new for your year (Victoria British offers even less than Moss for this item), but chances are you can reuse your old one. Remove and check the gear before ordering a new drive unit. Again, make sure the cable drive is not the culprit before going to have the unit rebuilt or replaced. It is available and is cheaper than the drive unit and, unless in very good working condition, should be replaced or cleaned and greased while you have everything apart. If your drive unit is damaged, you may have to go to a used unit, if just for a usable gear.
Also, if it is the drive cable that froze, plan to spend some time getting the wiper blade drive units out. Unless you have removed the retaining nuts recently, assume they are froze and may have to be split to get off. The drive unit casings are white metal and corrode badly in the threads. I found slotting the nuts part-way through with a Dremel tool and then tapping at the slot you cut with a drift or screwdriver will split the nut. It usually comes off after that, but be sure to check that the threads are in any condition to accept new nuts. Replacement nuts and gaskets are available fairly cheap (certainly cheaper than replacement drive units), but if the unit is too badly corroded to use, it would be a waste of money.
I hope this helps you. Good luck and let me know what you find.
Art Isaacs
Electrical Connections
Art Isaacs
Q: I need a little help. I was pretty good about taking photo’s of everything and putting stuff in baggies and labeling the bags.
My confusion now is that I only have one switch and it seems like the Pressure Failure switch (see the first picture below). I am surprised if I lost the Stop Light switch because was very careful taking this all apart. That is why I am not sure there ever was a Stop Switch. While it is not impossible, I am surprised I would have not taken a picture of it, put it in a bag and label it. I took the pedal box out, had it sand blasted and painted so I think I would have seen it and taken it out.
There is a threaded hole in the pedal box over the brake pedal so it seems like
there may have been a switch there. I just don’t remember it or have it
documented and the threaded hole may have been used in prior years.
My confusion is if you look at first picture below, the green barrel connectors hanging off of the switch plug neatly into the connectors on the harness wires (see second picture). The harness wire extends about another 1 ½ feet with a plastic connector at the end. I think the plastic connector may have plugged into the Stop Switch in the back of the pedal box. I am just not sure. The thing that further confuses me is that if I connect the two green wires on the harness it lights the brake lights! Since the switch in the picture definitely came off the Master Cylinder and since when the green wires are connected (touched together) the brake light turn on, l thought maybe it was a dual purpose switch. I am just not sure.
In either case, do the two green wires with the barrel connectors coming off the harness look familiar? Does the plastic connector at the end of the wire look familiar? Are the two barrel connectors for the Pressure Failure Switch and the plastic connector at the end for the Stop Switch?
I put a few other pictures of the car. Maybe a little boring but certainly more
interesting than pictures of my kids!!
Thanks for getting back to me, this is really helpful!
Robert Ditta
A: The switch in the first photo looks like the stop light switch. It is the same one as in my 73 and both Victoria British and Moss show the same item number for yours and my year cars. The pressure failure switch would have a top to match the connector on the harness you have.
I found the Pressure Failure Switch in the catalogs and it's location, which is where you have the switch in your picture, and this explains a lot. It is Victoria British P/N 8-3147 (74 1/2-75, about $20) or 7-424 (76-80, about $35) and it shows being on the master cylinder where your current switch is. The sketch is small, but it looks to be a mechanical switch. The top more closely matches your harness' snap-on connector.
Now, what I believe is mixed-up is that the stop light switch is now in the place of the pressure failure switch. The one you showed me is definitely the lamp switch. It should be removed and relocated to the location you identified on the pedal box and the original pressure failure switch found or replaced and that should sort the problem in one fell swoop. If the pressure failure switch is mechanical, as it appears, it is possibly a "dry" operation and should not leak if removed, so taking your present switch out shouldn't cause the master cylinder to leak or gulp air. You can minimize the exposure by being ready to plug the hole with your finger and put the new switch right back in. Since the switch is on the bottom of the master cylinder, as long as it does not run dry or the pedal pushed with the hole open, even if it does leak a bit, it should not suck air in. You can then top it up and move on to putting the stop light switch in the right position.
To test the stop lamp switch operation, it should be closed (complete circuit/lights on) with the actuator pin extended and open (lights out) with the pin pushed in. The 2 switches may work opposite (the pressure failure circuit open extended/closed pushed in), which is why they are not interchangeable.
I continue to find it amazing that the switches would fit in
the same size hole with the threads. This is not the only example of this I have
found and it is not confined to British cars. If one hole were 1/16" larger or
smaller, they could not be mixed-up. Good luck,
Art Isaacs
Battery Cut-Off
Switch
Art Isaacs
A battery cut-off switch is an inexpensive theft deterrent. It is also a good idea if you have one of those hard to find battery draining issues.
I installed the switch on a '79 at the back of the battery shelf, but slightly towards the passenger side to avoid the sight rise at the center of the panel directly above the differential.
Similarly on a '73, converted to a single 12V battery, the switch is on the same shelf, behind the driver's side (just back of the empty battery box) almost against the vertical panel at rear to avoid the battery box cover.
Plenty of room for wires and required drilling the one hole for the neck for the switch to come through from below in both cases. I connected to the ground wire side of the battery and used the original ground connection to the chassis, but found numerous other bolts that could have provided an adequate ground.
I have also seen them mounted on the vertical directly behind the seats. I am not sure of which switches those were and how much clearance for connections was required.
Low Oil Pressure
Art Isaacs
Low oil pressure can be caused by a number of things including cracked or blown
piston rings that allow exhaust gasses to blow by and mingle with the oil in the
sump. This thinned (and ruined) the oil and can cause oil pressure to drop off
rapidly.
A compression test is always a good idea. Just like a physical, you should
maintain a record of the compression yearly. It gives you a measure of internal
wear.
Some points that might also help you identify this as a problem:
- The oil smells of fuel or exhaust.
- It gets discolored quickly.
- You usually get excessive oil mist and leakage around the breather from the
excess pressure in the crankcase. In the extreme, oil can come out of the
dipstick tube or main seals.
- The spark plugs are wet or discolored from oil.
- The car can even be smoking from burning oil, which is getting into the intake
through the crankcase vent/PCV valve (depending on how your car is equipped) or
blow-by of the worn/damaged rings on the intake stroke.
Rings can be replaced with the engine in the car. Main bearings cannot. However,
if the rings are damaged that badly or so worn, the cylinders should be
professionally bored. While this can still be done with it in the car, I would
suspect all the wearing components' condition and want them replaced at that
time as well. Resultant work is still an overhaul with the engine removed.
It has long been established that the original 14" diameter X 4.5" wide wheels (or a stock offset up to 6.5" wide) and stock, unmodified MGB/BGT body will accommodate up to a 185/70-14 tire. The keys to this fit are the overall tire diameter, tire width and wheel offset. Within those parameters are many variations that can give very different ride and handling characteristics.
The designation tells you the whole tire story. "185" is the tire section width (across the tread), in this case 185mm, or about 7.25". "70" is the "aspect ratio" (how much of the tire is in the sidewall height versus the width, by percentage) or the relationship between a tire's section height and its section width. It is calculated by dividing the section height by the section width. When the section height is half of the section width, the aspect ration is 50. In this case, it is 70%, which means the sidewall is about 129mm or 5". "14" is the rim diameter, in inches. Though most tires are metric, the rims remain measured in inches. "Offset" is the distance from the edge of the rim to the centerline of the wheel; the amount the wheel is set-back or forward from the back side of the attachment to the axle (the description was worded this way as better for those of us using wire wheels). Too far back, you hit the inner fender; to the front, you can hit the body.
There are other designations for speed rating, service type and wear, but let's not get into those here. "R" is for radial and appears on almost all designations, so I've ignored it in this posting.
The 185/70-14 tires have relatively high side walls and ride softer and firmer than the original 155/75-14 tires the car came with, but might have more side-to-side movement than a more performance enthusiast might want. A firmer ride and less "squirm" in handling can be done by increasing the tread width and reducing the sidewall height. This can be accomplished by changing the aspect ratio of the tires, but to do that correctly, you should really change the wheels and "plus size" or you can effect the speedometer and transmission ratios.
For the sake of this comparison, we'll use the 185/70-14 as the base size. In reality, this tire is much larger than the original tires and has already effected your speedometer readings by about 4.5%.
A 185/70-14 tire has an overall diameter of about 614.42mm (24.19"). Just going to a 60 series tire to reduce the sidewall to make it firmer will drop this to 577.59mm (22.74"), which is 6%. It means your wheels will now turn more per mile than before and the speedometer will read almost 64mph where it had been reading 60mph previously.
Using a "plus size" tire would mean going to a 195/60-15, which has virtually the same overall diameter, 1/2" lower sidewall height (profile) for firmness and about 1/4" more tread width. Speedometer readings would not be effected, but it means going to 15" wheels.
Most tire stores have charts available to help sort this out for you.
Going too large or reducing the profile too much can have other potential problems.
Too low a sidewall and the rims are subject to bending at every pothole. Having little to do with MG's, my wife and daughter have similar cars, the newer of which came with 17" rims and 50 series rubber. The factory original 15"/70 series tires and wheels on the older car are still fine after nearly 70,000 miles. The second set of 17" wheels is already showing some damage, and only after a combined 40,000 miles for the 2 sets. I will be increasing the aspect ratio on new tires after straightening the alloy rims (yes, I now find there is a big business in this, not surprisingly), going from 50 to 60 series rubber, and hope that will give enough distance between road and rim to avoid further problems, without effecting the car's handling too much. Otherwise, I'll have to drop back to 15" or 16" rims.
Also, making the tires too wide can potentially damage the suspension and put strain on the bearings that the car was never designed for. Some of the "skip" or slid experienced with the old, narrow tires inadvertently helped avoid this and prolonged hard driving at the limit with very sticky rubber may cause damage to these items and could even cause axle or transmission damage and wire wheels to collapse in the extreme. Most of us do not drive our LBC's in the rain, but the wide tires are much more prone to "hydroplane" or raise the car atop water on the ground. The brakes are not that great to begin with, sliding on the water will only make it worse.
There is a good website to experiment with the different sizes. They have a comparison chart that allows you see, side by side, the differences. It also has a great glossary and index to study. It is www.1010tire.com and go to the tire size calculator.
I've had the clutch freeze on me over a winter's storage. I could not get it into gear without grinding or the car being engaged and moving. If I tried to start the car in gear, even with the clutch pedal fully depressed, it still rolled, even with just the starter. I chose to replace it. Engine out and the whole bit. I know there are ways to replace the clutch with the engine in the car, but they are not that easy and really only eliminate the need for the hoist. I have it planned out that I can remove and replace the engine/trans/clutch in about 8 hours by myself (I detailed the sequence for someone else and can forward it to you, if you want) and the engine removal gives a chance to examine and address other things as well. In this instance, I knew my clutch had considerable wear and mileage on it, so felt the effort beyond just "unfreezing" it worth it.
I have also experienced similar symptoms to what you describe and it turned out to be a failed clutch Master and/or Slave cylinder.
The system appeared to bleed and work much as yours does and there were no obvious leaks of fluid. Leakage at the slave cylinder is the most obvious clue there, but if the master is worn internally (piston seals), no external leakage will be apparent. This was the case in this instance, and it happened suddenly with the car sitting unused.
If you think your clutch/disc/throw-out bearing still in good shape and with a good deal more life to offer, I would suggest you test the system another way before attempting anything else. Try moving the clutch actuating arm manually. I removed the slave cylinder (just disconnected it from the arm and took the bolts off the bellhouse) and used a cable type come-along (light hoist), attaching the cable end to the arm where the slave cylinder connects and other end to the chassis. A jack might work as well. With the arm visibly to it's maximum engaged travel, start the car in neutral and try putting it in gear. Do not step on the clutch pedal. If it goes into gear without grinding or effort, then the problem is more likely hydraulic. If you still cannot, it is probably frozen with rust or some other mechanical problem.
Correct
Engine Oil And Low Oil Pressure
The correct oil for MGBs is actually a straight 50W. This is getting harder to find, but today's multi-grade 10W- or 20W-50 work as well, if not better. All cars drop pressure as they get warmer. While the pressure should be closer to 60psi when cold, 50 is not really bad for a 20+ year old car with 63,000 miles on it. Idling, the pressure can drop to about 30-40psi once hot, but you should be able to achieve 50psi or better once at speed. The previous owner of my car had worn the mains down to the shells and when I got it to run before rebuilding, it had only 11-15psi at idle and 45-50psi underway. It did not knock or show any apparent difficulties.
Castrol (and others) offer "high mileage" formulated oils not so much to improve the pressure, but to improve the lubrication the oil provides as wear increases clearances and causes pressure to drop. There are other additives that do the same, but these oils seem to work well at a reasonable price.
Mechanical reasons for low oil pressure are a bad pressure relief spring (but not really likely), worn cam or crank bearings, or oil pump wear.
Oil pressure dropping after running for a while is normal for an older car and changing to a multi grade, higher viscosity and/or oil formulated for higher mileage engines may help.
Backfire on Deceleration
Art Isaacs
If your car is experiencing backfire on deceleration there are a few things you should look at first. The good news, these for the most part just require some time and no real-special tools or expense.
First, have you noticed any change in operating temperature? The engine running hotter could potentially cause backfiring and be an indicator of other issues, including timing and other specs being out of tolerance.
Ignition wire condition - self explanatory.
Valve Adjustment: Keeping the valves "tight", or adjusted to the minimum cold specifications can result in clearances above tolerance once the engine warms-up, and the engine will run hotter now that Summer is in full swing. This can keep the valves open slightly or cause "float" that prevents the valves from sealing properly between cycles.
Points Adjustment: Recheck your point gap. Make sure the lobes are lubricated and even and that the shaft the rotor goes on is not wobbling (see next item). Wear or roughness on the lobes will change the gap quickly and effect the adjustments.
Timing Advance/Retard issues: Though the timing - both static and dynamic - may be correct, the various systems controlling the advance and retard of the timing while in operation may be faulty or out of spec. There’s a mechanical system of weights and springs that are subject to degradation and wear over time. There’s a vacuum system that has been especially know to fail as these cars get older (though the indicator here is more often poor acceleration and sputter/backfire under load) and then there’s a sliding plate beneath the points that can bind and move slowly or jam and not move the entire range necessary. You even have to be concerned that the screws provided in the tune-up kits are the correct length. Too long, and they will catch the lower plate and lock the whole thing up.
Put on a timing light and see how steadily it maintains the mark. Then bring the RPM’s up a couple of times (fast and slow) to watch how fast (and if) the timing advances and then settles back to the original mark.
These cars have almost all had some sort of distributor repair, modification or replacement. Even if what appears to a correct distributor may be in place, it could be from a different model, year or even make (i.e.: the 25D originally in my 73 was identified as belonging to an early Midget or Sprite). Though there may not be enough difference in the curves, weights and spring characteristics to make any real difference, if you recently changed yours about the time the problem started, I would look at it more closely.
Spark Plugs: Check the gap and for any build-up. If you’ve recently gone "hotter" or "colder" on your plugs, this could effect you as well
Exhaust System condition: I’ve got an old Monza system and judging by the sound, it must be beginning to wear-internally (it does sound wonderful, though). As a result, I do get a little rough crackle and burbble dropping off the gas or downshifting at speed. Some noise should be expected, but a loud, legitimate backfire or anything coming back through the carbs would indicate a real potential problem.
If it is both front calipers that are not releasing, first check the pressure failure assembly - a 4-way connection block with a sensor switch mounted on the fender just below the master cylinder. If the internal shuttle is stuck, it could hold fluid from returning to the master cylinder.
Most later cars did not have this assembly and had completely split front/rear systems. If that is your set-up, and , again, BOTH front calipers are locking-up, I’d check the master cylinder itself (front piston). Brake master cylinders are designed that they restrict the fluid back flow slightly to prevent jerky brake operation. Blockage, gunk or wear could cause it to act as you describe.
Here’s a crude way to check a system WITHOUT a pressure failure assembly:
- Disconnect the brake lines from the front of the Master Cylinder and the 2 calipers. Put clean rags on the ends of the flex lines at the calipers and jars or cans to catch the fluid.
- With compressed air, blow down from the top toward the caliper lines and see if it is clear. You do this first to clear as much oil and gunk out of the lines into the cans or rags away from the car to prevent damaging painted surfaces with the fluid. Check the rags for any real gunk or debris. Your car is many years old. There will be some dirt in there unless you just flushed the system. You are looking for stuff that could block the lines or pistons.
- Next, cover the inside of the engine compartment and any painted surfaces to prevent brake fluid from damaging them. Put a rag over the top end of the line near the master cylinder.
- Now use the compressed air to blow back toward the master cylinder end of the line. The rag will again catch any crud in the line, if there is any. You may also have to reconnect one of the calipers at a time to make sure the lines are clear.
- If they are clear, the problem is likely in the master cylinder, and it should be rebuilt or replaced.
It’s a bit of work and can be messy, but it should at least pinpoint the area of the problem. This would not work on a pressure failure system car as the valve would react as if a line failed and not give you a true reading as well as potentially damage the valve assembly itself. That should be dismantled and rebuilt or replaced by someone familiar with its operation.
The likelihood of a problem with both calipers at the same time is much less than that of dirt in the common lines or master cylinder.
If the car is pulling to one side, it may well be a caliper hanging-up, deterioration of a flexible line to the caliper or a mechanical problem with the pads. That would be more obvious to detect as it would be confined to that side.
Do not lower you convertible top, glass of plastic window when the top is wet, to avoid discoloration or other damage to the topping or inside backing.
Do not store away wet top boots or tonneau covers, to avoid discoloration and shrinking that can cause these products to no longer fit.
There are many possibilities ... first, check to make sure that you are getting spark and fuel? The simple things are: blocked fuel filter, broken engine ground, loose wire, dead fuel pump, collapsed or loose/cracked hose off the carbs - to name some of the obvious ones.
Does she crank over easily? If not then you should suspect dead batteries (dead alternator) or a bad battery connection or ground connection.
You need to insure that you are getting a spark to the plugs. We will assume that the timing is OK since it would be difficult to imagine that suddenly going bonkers. If no spark, then check the wiring at the distributor and coil for loose wires. Otherwise no spark usually means the points are bad/maladjusted or the coil has died (unusual). The spark wires do not usually die catastrophically. Also check the engine ground strap on the left motor mount. I had that fail on my then new 72 B in a rainstorm causing total engine shutdown and a tow to the shop. The girl I had with me at the time was not impressed. The key is make sure that you do have a spark at the plugs, but be careful about shocking yourself. Another possibility is a bad ignition key switch, but leave that for last.
If the car died suddenly, that often indicates a loss of fuel. Carefully remove the fuel line going into the front carb and place the end into a pint or larger jar. Turn on the ignition fully (do not crank). The fuel should pump freely into the jar, and you should hear a clicking sound from the rear (fuel pump). If so, then fuel delivery is not the problem. If not then probably the fuel pump has packed up. Fuel filters usually give warnings before plugging completely by causing fuel delivery shortages at high speeds, but idling just fine. SU fuel pumps can be rebuilt cheaply and with simple tools. I have rebuilt my original 30-year old pump three times and have just wired a transistorized switching system that should insure that I do not have to do it ever again.
If a hose has come loose from the carbs, that can lean out the mixture to the extent that the engine dies - check for loose hoses. Look for collapsed hoses, too. Some can put a vacuum on the carb float chambers which will cause near-immediate fuel starvation. That happened to me also. Make sure that the carbs have oil in the dashpots. Although sudden failure is not usually their problem, a lack of oil could render the carbs nonfunctional.
Q: The original specs for my 1974 MGB call for 155SR14 tires. The set on it has only 10,000 miles on them but they are 20 years old and the side walls are cracking due to age and the freezing that occurs while the car is stored in the winter. As the current tires are Michelins, I contacted the local dealer who stated a price of over $125.00 a tire for replacements, without including tax or mounting and balancing! Do you have any suggestions of a brand that might be less expensive?
Tim Beaton
A: First, you can get another brand, or Sam’s Clubs, for instance, sell Michelin tires at a discount, but they still pricey compared to other brands. B F Goodrich "Advantage" tires are also available at Sam’s club for about $50-60 each, mounted and balanced. Finding the 155-14’s may be the problem as they are not that popular any more. Your '74 can fit up to 185HR70-14 tires on the stock wheels without interfering with the bodywork. I have this size on wires on my '73 and the improvement in ride and handling is impressive. So you can also try going to a budget-priced more popular size (165 or 175 for instance) if you want to remain at or close to stock, or even an off-brand tire. At one point, I had a set of 185HR70-14 40,000 mile warranted "house" brand tires called "Euro P Metrics" from Pep Boys that cost about $180 for the set of 4 on sale, mounted & balanced. They were on the car for at least 3 years (on the disc wheels) without incident and, with the type of use I give the B, I really did not see any significant difference between them and the Goodyear "Eagle" tires I now have on the wires.
I hope that helps. Good luck.
Art Isaacs
Battery Replacement
by Konrad Crist
This is an easy one. Even most purists will agree that going from the twin 6-volt batteries to one 12-volt battery is an acceptable move. A Type 26 12-volt battery should fit in the passenger-side battery box. Remove the old 6-volt batteries, the connecting cable and the negative ground cable on the driver’s side and put the new battery into battery box. Check the box for soundness first. Many new batteries have little tabs sticking out from the bottom of the battery case. These may have to be clipped off to get the battery into the box all the way. Of course, be sure to measure the width and depth of the old and new batteries making sure that the new battery will fit. The battery box is deep enough so that you should not have any height problems. Your battery hold down, however, may need to be replaced. I use a non-conductive, PLASTIC-hooked bungie cord stretched and wrapped around the box and battery. Not very pretty, but then, who sees it?
Attach the positive cable to the battery. Buy an approximately 24 to 30 inch long black battery cable with a spade lug on one end (you better measure first). Attach the black cable to the negative battery terminal and route the spade lug end over and an attach to the negative attachment ground in the driver’s side battery box. That should complete your connection. Modern 12-volt batteries are smaller and more powerful than the old 6-volt batteries, don’t require maintenance (much), and last much longer with less trouble. If you don’t already have a single 12-volt battery installed, you will be glad you did!
Overdrive Repair
by Art Isaacs
Remove the gearshift from inside the car by taking off the gearshift boot and removing the 3 bolts to release the shifter. Jack the car up on stands fairly high - rear higher than front. The car should be at least high enough for you to get under and work easily. Remove the propeller (drive) shaft from the car (4 bolts at each end). Mark the flanges for alignment so they go back in exactly the same position. Support the transmission with a jack and remove the rear transmission support and brace, if equipped. Lower the transmission to rest on the forward (fixed) crossmember. Remove solenoid wires (mark locations or photograph, as dirt and grime hide wire colors). Remove the (8) nuts from the studs that secure the overdrive to the transmission housing and ease it off the mainshaft. If you still have clearance problems, you might have to undo the motor mounts and pick the front of the engine up slightly, but I do not believe this will be necessary.
The fun part is having the patience to line the internal splines of the OD unit back up to the mainshaft. This will take some doing (even with the unit out of the car, standing on end and trying to line everything up vertically, this is a chore), but don’t force it or try to pull it in with the studs by force or you could jam the internals or crack the housing at the flange. All else goes back as removed.
Of course its is both more work and at the same time easier with the unit out of the car. This just does not require a hoist or the dismantling of the engine’s ancillary equipment to do. Hope that helps.
Brake Drums
by Norman Nock, Technical Staff
This article covers the basic workings of the brake drums and shoes. The
pressure of the brake shoes against the drum starts with the force applied to
the brake pedal.
The shoes are pushed out against the brake drum. One end bears against an anchor point, or heel, the other end is pushed out by the wheel cylinder. When the drum is rotated the friction force between the brake drum and the lining tries to turn the shoe around the anchor point. The shoe is then forced more strongly' against the drum, like a wedge. This is known as self-energization.
The wedging action starts at the toe, or the wheel cylinder end, and keeps increasing as it nears the anchor point. If the drum is revolved backwards (reversing) there is no self-energization. Therefore, you have less braking when going backwards.
The rear brakes have one leading shoe and one trailing shoe. Unlike the front brakes that have two leading shoes. When the brakes are applied the wedging action is only on one of the shoes, depending on the direction of rotation of the drum. The reason for this type of brake is so you will have stopping power by always having a leading shoe, and when using the hand brake you will always have a leading shoe which ever way you park on a hill.
Lucas Generators
by Norman Nock, Technical Staff
If your ignition light comes on when driving, you have lost your fan belt or
your generator has possibly stopped charging. To check if it is the generator
you remove both wires from the generator, and with the engine at 1500 rpm join
the two generator terminals together with a small screw driver, then quickly
pull the screw driver away from a terminal. If you get a thick blue-orange flash
the generator is o.k.
With no flash, remove the generator band and inspect the brushes for wear. If the brushes are worn the spring could have bottomed on its hold; an emergency repair would be a small shaped piece of wood under the spring to cause brush to press on the commutator again.
Without the generator charging, the battery will go flat in about three to four hours driving (no lights). If you are with other Healey people you could trade batteries with other cars that could keep you supplied with a charged battery.
If your problem was the generator and you rebuild it, don't forget to remove the field coils to inspect the tape.
Restoration - Painting your MG
by Jim Napoleoni
As technical advisor for the AMGBA I have received various inquiries over the years relating to color, procedures, and general restoration. Although not an expert body man, my 15 years experience with DuPont Automotive Finishes makes me an authority on prime and paint systems. My project car is a 1972 MGB was purchased 1993 in St. Louis and made its debut in Chicago in 1998 painted single stage BRG. The nuances of replacing dash, wiring,.. leaves the car somewhat unlawful for street use but it is mechanically sound and the neighbors say it looks great.
With increasing Local, State, and Federal regulations aimed at reducing air pollution, traditional products used to restore and repair our automobiles have changed dramatically in recent years. In some areas of the USA local authorities have limited over the counter paint sales to hobbyists. However in most areas, automotive paints and primers are still available at your local automotive paint jobber. Your paint distributor may be an excellent source of advice.
Safety: Generally speaking, modern automotive paints are much better that they were way back when. Although many traditional paints such as acrylic enamels and lacquers are still available; better finishes are available. Modern paint additives significantly improve durability. Acrylic urethane single stages, and base / clear finishes used with urethane clear coat all contain additives that are safe to use only if one is isolated from paint over spray using a supplied air respirator. Failure to use a supplied air respirator while painting (or observing) exposes one to harmful fumes. If you cannot be so equipped leave painting to the pros. Material budget for single stage should amount to $400 - $600 Depending on color. Add an additional $175 for clear coat. Always visit label directions for mixing, application, and safety direction.
Color: Which BRG are we looking at? It seems that there are as many shades of various colors as there are cars. Paint distributors have new computer technology that allows them to "read" colors with instruments such as DuPont's ChromaVision. Given a viewable surface and the "correct" color sample the computer can locate an existing color formula, or generate a complete new mixing formula based on the digital color position. When I was restoring my re-sale red 'B" to the original BRG several years ago I pulled off the dash and read the original BRG position from under the dash using a ChromaVision. This area has never been exposed to the degradation of the sun's ultra violet (UV) light and is considered not faded. Although I consider my B's color position on the mark, it is always a topic of discussion at shows.
Old chip books are a great source of color information. Most vintage colors have been developed in modern paint chemistries. Old Centari color positions have been duplicated in modern single stages, and base / clear options. OE production has been traditionally single stage but new base / clear systems are more durable and match very well. Always have the color sprayed out and approve it yourself prior to painting. Color is in the eye of the beholder.
Restoration: Most restorations involve stripping off the old finish down to the metal. If your vehicle finish is in good shape you may elect to save on expenses by sanding, sealing, and painting. This method is generally OK if there is limited rust, and you are working on the OE paint, not on top of a re-spray. If this is the third paint job strip it.
Preparation: Once down to the bare metal and bodywork is complete, remove all surface contaminants prior to priming with a solvent wipe. Using the two-rag system soak a clean towel with a cleaning solvent (DuPont 3939S, or 3909S) and wipe down the car. While the car is still wet with solvent, wipe off remaining residue with a clean towel. This process is your key to success as any residue remaining on the surface will allow rust to form even under the best primer; ruining an otherwise excellent paint job. (Even fingerprints can re-appear under a good paint job). Prior to application of primer tack wipe the car.
Primer: Primer provides corrosion protection and adhesion. Over the primer, a primer-surfacer is usually applied to fill sand scratches in bodywork, and to allow for sanding a smooth surface. Many professional shops also apply a sealer just prior to paint.
Primer Options:
Self-etching primer: This classification of direct to metal primer is two component. (DuPont VariPrime) primer is reduced down with thinner that also contains a mild acid. The acid bites into exposed metal and the primer flows into the etched substrate. One mil dry film thickness (DFT) should be applied with two medium wet coats. Primer surface is then applied.
Epoxy: This product classification is an excellent option if one chooses to perform a two-stage metal treatment step after the final solvent wipe. Epoxy primers take a little more attention and prep, but perform somewhat better than the easier self-etching option. Again, primer surfacer is applied over epoxy primers (DuPont Prime 'n' Seal).
Primer Surfacer: Urethane primer-surfacer is the new recommendation for high performance and long-term durability. Many restoration houses have moved into this technology, but many "resto" shops will still use inexpensive lacquer primer-surfacer. Urethane products such as DuPont URO-Primer provide excellent fill, sandability and product performance. You can expect much better chip resistance using urethane vs. lacquer. Do not "fix" bad bodywork with good primer-surfacer. Finish sand bodywork using progressively finer sandpaper grits i.e. # 80, # 180, # 320, and # 400. Do not skip from # 80 directly to # 400 grit. Use two - four coats primer surfacer allowing primer surfacer to flash dry in between coats for a minimum of 15 minutes. Do not pile on primer surfacer as this will lead to poor appearance when painted.
Sealer: Most quality shops will apply a uniforming sealer just prior to top coating. Again two chemistries are available. Epoxy (DuPont Prime 'n' Seal) and urethane (DuPont ChromaPremier Sealer). Urethane sealers are preferred.
Topcoats: As discussed above topcoat choices abound. Choose between single stage acrylic urethane (DuPont ChromaOne), or base /clear (DuPont ChromaBase). ChromaOne single stage is a much-improved coating compared with acrylic enamel (Centari). MG's have been painted at the factory with single stage paints so to be true to the OE use a single stage.
Modern OE finishes are base / clear finishes. MGF production is painted with B / C. If you are looking for a more durable long lasting finish use B / C. The key to this outstanding durability is the choice of clear coat. Medium solids clears mandated by federal EPA are durable, fade resistant, and easy to maintain (DuPont V-7500S). Historical colors have been developed or can be generated using a colorimeter.
With all that said here is what I laid down on my restoration followed by approximate usage:
1. Vehicle stripped to bare metal.
Chemically then finished with DA sanding.
2. Solvent wiped with DuPont 3939S. One gallon
3. Two medium coats DuPont VariPrime. Two quarts ready to spray (RTS)
4. Two double coats DuPont URO-Primer. Four quarts RTS
5. Wet block sanded URO-Primer with # 400 (starting with #150).
6. ChromaPremier Sealer applied in one medium coat. One quart RTS
7. Three wet coats DuPont ChromaOne acrylic urethane. One gallon RTS
If I were to use base / clear I prefer
DuPont ChromaPremier base color followed by two coats V-7500S clear coat. Never
sand refinish base color prior to application of clear coat. Peeling of clear
from color may result. If you must sand the color coat re-apply a coat of color
prior to clearing.
Jim Napoleoni
email:
james.j.napoleoni@usa.dupont.com
(815) 459-0104 fax / phone
Tire Rotation - When and Why
by Mike Martinez, Martinez Motorsport
If you want to get the most life out of your vehicle tires, make sure to rotate them every third oil change, or every 9,000 miles. The purpose of rotating the tires is quite simple. Because the front wheels do the steering, and do not always travel in a straight direction, they will wear out much faster that the rear tires if not properly rotated.
A set of tire should last from 50,000 to 60,000 miles if properly maintained and rotated. If tire rotation is neglected, the front tires can wear to the steel belts in as little as 20,000 miles, in which case they will have to be replaced. When rotating the tires, it is also important to set the tire pressures, and torque the wheels to the specified tightness.
As far as wheel alignment is concerned, have it checked every two years to make sure everything in the front end is in check. A quick inspection is all it takes and a road test is a good way to judge the alignment condition. If the steering wheel is not centered when driving straight, or the car has an excessive pull to either the right or left, have it put on an alignment rack and put back into proper specs.
Here's a tip from Mister SU: Master mechanic
Joe Curto would like to pass on the following very useful information to our
members.
To all owners of MGs who have oil filters that spin on from the top. This
includes all late model MGBs and those like myself who have converted over to
this much more convenient installation.
The standpipe that goes up through the middle of the oil filter is approximately
3" high. Many enthusiasts have long believed that if you use a 5" or 6" high oil
filter, you will have almost twice the filtration. The truth is that if a high
oil filter is used, every time the engine is turned off the oil in the filter
will drain down to the top of the standpipe. This will leave the top
two or three inches of the filter empty. This means that every time you start
your engine, the filter has to fill up again before the engine gets any oil.
This is the same as starting your car for the first time after you have changed
the oil and filter. For the first 10, 20 or 30 seconds, the engine has no oil
pressure. Therefore, only short oil filters should be used.
Many thanks to Joe for this very valuable tip. It must be mentioned that Joe
expertly rebuilds much more than SUs. He also does generators, windscreen wiper
motors, distributors, MGA directional signal switches and much, much more. No
one does a better job. For the few members who don't know him, he is located at
22-09 126th Street, College Point, NY 11356. That's Queens. His phone number is
(718) 762-SUSU (762-7878).
Wire Wheel Inspection
by Norman Nock
The word "clunk" is a very good description
of the sound made by a worn wire wheel hub or wheel splines, but there's no such
word in Webster's. The closest word is "clink", but "clink" does not have the
right feel to it when spoken.
Damage to the wheel and hub splines is usually caused by drivers who do not know
a problem can develop until one day they have a flat tire and discover that they
cannot remove the wheel due to rust. Many service stations have removed a flat
tire from the rim with the wheel still on the car as they couldn't remove the
wheel!
When the British sports car was a common sight on the road in the 1960s, this was the time when deterioration from neglect was taking place. Inspection of the spokes, where they go into the hub, would show rust coming from the hole, but drivers would not spend the money to have all four wheels removed and hubs and splines cleaned with a strong wire brush and solvent. Twenty years later you are now the owner of these rusted, deteriorated, neglected hubs and wheels. You could be one of the unfortunate drivers who will have a wheel fall off unless you inspect them very carefully and replace all worn parts.
If, due to wear, the wheel moves on the hub every time you apply a load via the brakes or engine, and you hear the proverbial "clunk", now is the time to inspect them. Don't just use a bigger hammer to knock them on tighter. If you do you will strip the threads on the knock-offs and the wheel will fall off anyway! Instead, remove a wheel and clean the splines on the inside of the wheel. Now clean the splines on the hub which is bolted to the brake drum. Use a strong wire brush and solvent and clean them until you are down to shiny metal.
Now you are ready to inspect the splines. Each individual spline should have a "flat spot" on the top (see diagram). If the flat spot is gone and you have a knife edge, the hub and/or the wheel will need replacing. Check the edge of the splines with the side of your thumb. If the splines are sharp they need replacing now! Wear will show itself in the center of the splines, and then one day you'll need your brakes for an emergency stop. The brake drum will stop, but the wheel will slip on the hub and the car will pull to the left or right. Your imagination will tell you the consequences.
Also, when a wire wheel with worn splines turns, it can wobble. Under the right conditions it can cause the knock-off to turn itself off working on a ratchet principle. Make sure the threads on the knock-off and hub feel snug when they are screwed onto each other. Note, however, that there will be just a very little bit of wobble when the knock-off is screwed onto the hub without the wheel on.
If you can't remove your wheel in the usual way due to rust, take it to a shop that has a puller for just such cases. When all else fails, you will have to cut it off with a torch.
Finally, to check the tightness of individual spokes in your wire wheels, jack the car up to remove the weight from the wheels. The wire wheel must hang down on its spokes. Next, tap them to listen for the dull sound of a loose spoke.
One complete set of wheels and hubs might seem expensive, but have you ever checked on how much it would cost to replace your car? Then there are the hospital expenses to consider .
Mysteries of Motor Oils
by Theodore Glaser
Did you know that your motor oil does not 'wear out'? No matter how black it looks, it still lubricates.
Before World War II it was a common practice on farms (and possibly other places) to take the oil that had been drained from any motor and deposit it into a 55 gallon drum that sat up in the rafters of a barn. A stout piece of rope (at least 1 inch in diameter) long enough to reach from the bottom of the barrel up over the top and down to ground level was soaked in the old oil until it was saturated. One end of the rope was tied around a suitable heavy object and remained in the barrel. The other end was extended out of the barrel and allowed to hang down to ground level, with the end in a bucket. The oil would drip into the bucket, and be returned to the drum in the rafters. This process would eventually clean up the oil, as it was a siphon and the dirt in the oil was trapped in the rope. When the oil started flowing 'clear' it was put back in the tractor/car/mower or any vehicle that needed it. The only time oil was 'lost' was due to bad rings/valve guides which burned the oil. Eventually the rope became full of the dirt and had to be replaced but hundreds of gallons of oil had been 'cleaned' in the process.
The number that designates the motor oil's viscosity is a reference number that applies to the slope of the curve that results from plotting rate of flow thru the 'standard size hole' vs. temperature (-40§ F to +275§ F). The flow rate units used are Centistokes/second. The curve is for an 'ideal' flow of a single viscosity oil. A "5" weight oil is extremely thin and has a fast flow rate at the various temperatures involved. A "50" weight oil is extremely thick and thus has a slower rate of flow all along the curve. Lower viscosity is required in cold weather for reduced drag during starting. Higher viscosity is required for high temperature operation in order to maintain sufficient oil pressure when the motor has warmed up and the clearances have increased (except in Mazda's rotary engines, where clearances decrease so the oil pressure goes UP).
Multi-viscosity oils have as part of their additive package an viscosity index 'improver' that will allow the same oil to meet the low temperature flow rate of a low 'weight' oil and the high temperature flow rate of a high viscosity oil. There is no apparent change in the oil's consistency. If you pull the dipstick out of a hot or cold motor, the same few drops will run onto something clean.
Before WW II, oils were designated 10W, 20W, then 20, 30W, 30, 40, etc. These oils were "Non Detergent" (see "ML"). The letter "W" in the designation means that the oil is suitable for Winter service. From this the "W" was applied to the multi-viscosity oils. Note that the containers are usual marked "10W-30". One of the problems many people experienced with the very first multi viscosity oils was that after a period of time, the additive package would deteriorate, leaving one with the original (high) flow rate, low viscosity oil. One thousand mile oil change intervals were normal, mostly to remove the accumulated crud and acids. About that time, oil pressure gages were replaced with "idiot lights" and what people didn't know didn't bother them.
With the onset of more modern engines, the additive packages were improved and oil service ratings were revised as well. Some of this was of course learned from the operational results obtained during WW II. The service ratings were developed by the American Petroleum Institute (API). They progressed from ML (motor, light), thru MM (motor moderate), MS (motor severe), DG (diesel general), to DS (diesel severe). Oil change intervals went to an unbelievable 2,000 miles. Each increase in rating required a better additive package which included better detergents, anti-foaming, acid neutralizing, anti-oxidants and surfactants that keep particles in suspension if the filter doesn't catch them. A byproduct of the increased detergents was an increase in oil consumption and excess leaking in older cars. The detergents were doing their job and cleaning out the crud built up from years of use of non-detergent oils. These detergents and additives are the part of the oil that becomes "worn out".
In the 50's the rating information started to be prominently displayed on a can of oil. A can of 10W-30 had all the 'good stuff' and it's API service rating was all inclusive (MM-ML-MS). This eventually was upgraded to include the DG & DS specs.
With the onset of emission controlled engines of the '70s, fewer combustion byproducts leaked past the rings and change intervals went to (gasp) 5,000 miles.
Today's engines run hotter and have extended oil change interval recommendations as high as 15,000 miles. The need to change oil is still a function of deterioration of the additive package and removal of the fine stuff (less that 1 micron, 0.0039 inch) that can not be trapped by the filter. This is the stuff that turns your new brown oil to black. Current BMWs (and probably other cars) have a 'countdown to oil change' meter as part of the engine management computer system. It analyzes the operating history of the engine and displays the recommended miles to next oil change. The number starts 15,000 miles. It decreases as the car is driven 'casually' but increases as the car is driven 'aggressively'. This is due to the fact that the oil is consistently 'hot' and the contaminants that consume the additives are driven off by the higher temperatures.
Synthetic oils are a different story. These should be called 'lubricants' as there is no oil in them at all. Their development history starts with the requirements of gas turbine (jet) engines used by the military. Ordinary 'oil' products were unsuitable due to the temperatures involved as well as the extremely tight clearances. The first synthetic 'motor oil' on the retail market was sold under the "Prestone" brand, manufactured by Union Carbide in 1959. Consumers were not happy because of very high consumption and leakage. The engines of that era were not ready for the product and it was withdrawn from the retail market. A similar problem occurred when people tried to add "Mobil 1" to their engines when it was first marketed. There were disclaimers on the packages, warning consumers that 'conditioning' of the motor' was required. The industrial market for synthetic lubricant flourished as it was used in turbines, stationary engines and of course jet aircraft.
On a personal note, the '59 Sprite that I raced in H production from 1964 - 1966 used Union Carbide synthetic lubricant instead of motor oil. I had a friend who worked at Union Carbide's research laboratory and he gave me some to use. After each race I would withdraw about two ounces and send it in for analysis. Over the course of three seasons the lubricant did not deteriorate to the point that it required replacement. It was still 'clear', indicating that no contamination was present and that the oil filter was doing its job. During a mid-season cam change the head was removed. There were no carbon deposits in any of the combustion chambers, only a gray film that could be wiped out with a rag. The oil pressure was consistently 40psi at idle and 65 psi as soon as ~1500 rpm was reached. The viscosity equivalent was 15w-60.
The newest oils have API
Service ratings of SH, SG/DC, CC, SF and SJ. What do you need for your car?
Start with the owner's manual. If you drive on short trips in cold weather,
change the oil at the onset of the cold weather, so you have a 'fresh' additive
pack to face the season. When the warm weather comes, check the 'transparency'
of the oil. If you can still see the dipstick thru the oil, you are probably OK.
If not, change it. Obviously, if the recommended change interval has expired you
should change it anyway. If you are a 'racer', you need to monitor the oil
temperature. When it starts pushing 275§ F, start thinking synthetic or
commercial blends of regular and synthetic. Don't try to blend your own.
When 'oil' is said and done, take it to a recycling center. Many auto parts
stores offer recycling as well as some of the "Quick Change" lube franchises.
Squeaky Brakes?
by Norman Nock
There are certain frequencies (noises) that humans react negatively to like a baby crying, sirens and screeching brakes. The noise from brakes is always there but is dampened out by the large mass of the brake system components but the noise becomes noticeable when components wear. If your hair stands on end when you use your brakes something should be done to stop the noise. When your front brake pads are down to 1 / 16' they should be replaced. The brake rotors should also be ground when you replace brake pads to help prevent any noise. The minimum thickness for brake rotors is .325". Brake shops will not turn your rotors less than minimum. When replacing brake pads the locating pins and shims should be replaced. A kit made by Girling is available called a "Squeal Deterrent Kit" that includes pins and shims. The shims should be lightly coated with a product that is made for British cars called PBC. Poly-Butyl-Cuppysil, # 153245, looks like brown tooth paste. Other products are available made in the USA. Remember, if all you do is replace the brake pads you could still get brake squeal. Rough rotors will file and scrape away the brake pad friction material, and could cause clicking, thumping or knocking when brakes are applied. A good test to determine the quality of the finish on a rotor is if you can run a ball point pen across the turned surface making a solid line. If you get dots it is not a fine enough finish. The ideal finish is 40-50 RMS "root mean square" - the difference of peaks and the valleys. Rotors should be sanded to remove the peaks after grinding to give a nondirectional surface. Clean rotors with a commercial brake cleaner, or soap and water. Rotors will rust very quickly after they are cleaned unless the vehicle is put into regular use. If any product is put on the rotors to stop them from rusting it would have to be cleaned off before the car is put into service. Here's a summary of what can cause brake noise:
Rotors need to be ground. Wrong kind of friction material. Loose fitting calipers, bolts or abutment. Poorly fitted pads. Shims missing. Grooved rotors. Loose fitting pegs. Foreign material embedded in pads. Small rock touching rotor.
Also check the felt pad and adjusting peg on front and rear drum brakes; rear drum brakes on cars fitted with front disk brakes (Figure 1). Use PBC to lubricate the felt pad, all metal to metal moving parts between brake shoes, backing plates, and wheel cylinders. Do not put PBC on linings. Replace dust seal #BTC 171 to help keep foreign materials out.
Backing Plate Adjusting Peg: To adjust the peg, back it off until it does not touch brake shoe. Have your helper hold pressure on the brakes. Screw in peg till it just touches the shoe then lock into place. Brakes should be worked on only by qualified mechanics.
MGB Suspension Rebuild
by Art Pfenninger
Battery drainage problems
by Luis Azan
As some of you may have read, I have been helping one of our members with a problem battery drain problem. I discussed how to check for a drain in our earlier postings. In case you missed it, we are checking for a key off draw by placing a test light in series with the battery's negative post and the negative terminal connection for the car. The light came on when placed in series with the battery. That tells us that we have a key off draw. We are now down to the diagnosis of the draw. Here is a very short list of things that may cause a key off draw.
First, if you have an aftermarket stereo in your MG, (and who of us doesn't),
the stereo will cause a
little key off draw. Usually it will measure less than 20 milliamps as measured
with an ampmeter. If you have the original Lucas clock in your car, if so
equipped it will draw another 10-20 milliamps. Now we are up to about 40
milliamps draw.
Factor in another 20-30 milliamps for corrosion and dirt on the battery and
terminals. At that draw rate, a fully charged battery will only last about one
week before it is completely dead. A weaker or older battery will die in a few
days to a few hours at that discharge rate.
The main killer of MG batteries is the alternator or, dynamo". If one of the internal rectifiers shorts to ground, you have a nice path to discharge the battery at about a 150-500 milliamp discharge rate. Lucas rectifiers are built well but over time the rectifiers may fail. The only correction is to replace or rebuild the alternator.
Placing a battery switch in the car, and turning the battery off when not in use, is a very good way to preserve your battery's life. I have one in my car and now the member I have been helping has one.
For more detailed instructions on how to diagnosis a key off draw, or any other electrical problem, please email me. I'll be happy to assist in any way I can. Luis Azan at email: rolls_guru@yahoo.com
On the Subject of Oil Pressure
by Norman Nock
This is an article about that illusive oil/temperature gauge on the panel of your MG. Maybe if we didn't have it, we wouldn't have a problem. But we do have it and these gauges cause more controversy than all other instruments put together.
After reaching operating temperature engines in good condition should show 60 lbs of pressure at 3,000 rpm and at idle of 600 rpm, the pressure should drop to about 35 to 40 lbs.
If you are inspecting a car that you are thinking about buying, be alert to
one possible trick. An unscrupulous person can obtain, reasonable oil pressure,
even in a clapped out engine, through the addition of very thick 90 weight
differential oil. If you have any reason to suspect trickery, check the
dipstick. The correct type of oil will quickly drip off the dipstick. Smell the
oil. Differential oil also has a very distinctive odor.
If your pressure at idle drops to below twenty lbs. you could have a problem, even though you still get a good pressure reading when underway. The high end of the oil pressure can be increased even on an old, worn-out engine by various means, but a low idle oil pressure will give it all away every time. In particular, if the pressure drops rapidly with only a slight decrease of rpm you should do something about it right now.
Check the Gauge First
Many owners, very concerned about a low idle oil pressure have taken that big
step of having their engine completely overhauled, only to find that the idle
pressure is only a little higher than before.
If you have low oil pressure, first do what we do. Look for the obvious. Is your gauge telling you the truth? Have a quality professional test gauge hooked up in parallel with your own gauge on your car. Then go out on a good long road test and see if you really do have low oil pressure. Or is it only your gauge giving you an incorrect reading?
High Oil Pressure
If your oil pressure runs 75 lbs. or higher on a continuous basis and you have confirmed that the gauge is reading accurately, don't think that if high pressure is good, higher is better. The problem with high pressure is that the quantity of oil coming from the rod bearings is so great that the piston rings can't stop the oil from getting into the combustion chamber. Also the rocker arm bushes and shaft are usually worn and the increase in flow from the rocker arms can cause oil to get into the combustion chamber by flowing down the valve guides. The source of this problem is usually the oil release valve.
Low Oil Pressure
If you are sure you have low oil pressure - 20 lb. or lower at 600 rpm - you could have the start of a serious problem which should be diagnosed and corrected as soon as possible.
Change your engine oil, remove the oil filter, and make sure that the necessary spring, plate, seal and washer are fitted below the filter element as shown in the picture in the factory service manual and parts book. Replace the oil filter and recheck your pressure again.
If you still have low oil pressure, check your engine temperature with a thermometer placed into the top of the radiator to check the accuracy of the temperature gauge. If the running temperature is over 200 degrees F. this will cause the oil to become too thin for efficient lubrication of the bearings and will show as low oil pressure at idle.
If the temperature is within the acceptable range, 165-185 degrees F. remove the valve cover. If you have oil springing up from the rocker arms and splattering all over the carbs, you have found one of the many reasons for low oil pressure-a worn rocker-arm assembly. If there is nothing else wrong in the lubricating system, a rebuilt rocker arm assembly could increase your oil pressure up to five lbs.
If your car has been equipped with an oil cooler, this will lower the oil pressure, due to the friction of the oil that is now going through extra pipes, hoses, and tubes. You may need to fit a stronger spring to the relief valve. Nevertheless, to do further diagnosis, you will need to disconnect your oil cooler lines.
There is nowhere else to look outside the engine. At this point, a professional shop would remove the oil pan to find the cause of your low idle oil pressure. With the oil pan removed, they will use a specially made container that is half full of oil and holds a steady pressure of twenty pounds. This tool is joined to the oil gallery via a flexible pipe, and oil under pressure is applied to the engine's lubricating system. The cause of low oil pressure can now be observed from the various bearings within the engine. Steady streams of oil from any of the bearings will show excessive clearance at that point and the cause of your low pressure.
The only way to get carbon and other harmful pollutants out of the oil is to drain it, and replace the oil and filter. The expense of an engine job, compared to the price of an oil change says clearly: "Change your oil regularly."
You don't have to have this tool to press on, however, Remove the oil pump and screen, inspect the oil screen to see if the oil pan has squashed it. If this has happened, it is possible that the pick-up on the oil pump is restricting the flow of oil to the pump, causing low or no oil pressure. If your oil pan is damaged, it should be removed and repaired. Damage to the oil pan can be seen by a visual inspection by Just looking under the car.
The oil feed pipe from the pump to the block should be inspected for cracks at the point of contact with the nut.
Strip and clean the oil pump. Any swirl marks on the inside of the pump body that can be felt with the finger, or marks on the impeller indicate that the pump should be replaced. Checking the pump clearance with feeler gauges can only measure the high spots (like the wear spots on ignition points).
Remove one rod bearing. If the bearing surface is in good condition, it will have a flat dull gray color and will feel very smooth when you scratch it with your fingernail. If the surface of the bearing is very rough, or is showing a bronze color, you have found a serious source of low oil pressure. There is only one fix to this problem and that is that the crankshaft will have to be reground.
The same inspection can be made of the main bearings, but only remove one cap to inspect the half-shell. Do not take off more than one at a time, and do not try to remove the top half-shell; you might not get it back on again.
Mechanics have used fine emery cloth in the past to give a smooth finish to a worn crank journal, but you should not do this. You will not solve your problem, but rather will only postpone the inevitable.
The bearings on the cam shaft can't be inspected at this time, but if the crankshaft journals are worn, expect to find worn cam bearings.
Oil Changes
If you have invested money to rebuild your engine, or the engine you now have is in good condition, change the oil regularly. The only way to get carbon and other harmful pollutants out of the oil is to drain it, and replace the oil and filter. The expense of an engine job, compared to the price of an oil change says clearly: "Change your oil regularly." I change my oil every 1,500 miles and the filter every 3,000 miles.
Questions and Answers
Q. When I start my MGB after not using it for a few days, I hear a light
knocking that goes away as soon as the oil pressure comes up. What does this
indicate?
A. The noise you hear may be a worn rod bearing that has developed too much
clearance. You most likely have a similar noise at about 2,700 rpm when you
accelerate in low gears. Do not continue driving until the cause has been found.
Q. I have an oil leak under my air filter of my rear carburetor. Where is the
oil coming from?
A. The oil is most likely coming from a worn rocker shaft. The hole in the top
of the rocker arm is spurting oil into the breather pipe on top of the valve
cover and along the breather hose into your air filter.
Carpet Kit Installation
by Art Isaacs
I have installed a couple of carpet kits in MG’s and other cars. It’s really not that hard. Victoria British used to put out an interior installation pamphlet occasionally that showed carpet and seat kit installations. That would helpful if you could find a copy.
To start with, you’ll need a sharp carpet knife with extra blades, a sharp awl or old fine Phillips screwdriver to help locate bolt holes, wire brush, a good shop-type vacuum cleaner (or any with a hose attachment), rags, glue and brushes. I prefer to use 3M brush-on Contact Cement (a quart should do) and a couple of throw away brushes, though I do keep a can of Trim Adhesive spray handy for later. I also have some Lacquer Thinner around as it does the best job of cleaning-up spills and spots of glue. I would also advise to get some latex gloves as this stuff is sticky and you do get it on your hands.
First, remove the seats, seat belts, consoles, door weather stripping, map pocket, front kick panels and rear side panels. There’s also a small panel behind the front (radio) console at center that may or may not be in your way. The center back panel is not in the way of this job. Remove the original carpet. It will probably come out easily, though if it’s truly original, not in one piece. Older models had some rubber pieces on the sills and around the console. They now sell the replacements, but I do not think the kits provide them. If they are in good shape, you might just want to leave them. Chances are, they’re shot and will come out in pieces. The old glue will be dry and dusty. Be prepared to vacuum and brush a lot. The cleaner you get the floor, the better the glue will hold the new carpet in place. Also check the captive nuts and bolt holes for corrosion and that the nut are still secure to the floor. It’s a lot easier to fix this now than after you’ve install your carpet.
Lay the new carpet in place to check fit and the alignment of holes for the gearshift, wires, seat belts, etc. Some kits I worked with only had the major holes punched (i.e.: gearshift). Items like the seat rails, seat belts, etc. would have to be located and opened up after installation. Now is the time to be to see if the holes exist and are in the proper place. Also to see how much trimming may be necessary. If they don’t exist, it is actually easier to do this, and, unless excessive, all the trimming once the carpet is glued in place. Whether all the holes are there or not, it’s always a good idea to take measurements locating all these smaller holes. I made a sketch of the floor and started the measurements from the same end - the rise to the battery box shelf. I then measured the distance forward to the seat belt securing bolts, as well as the distance up from the floor. Next, again from the rise, I located the back bolts of both the seat tracks and the distances of both the front and rear bolts from the drive tunnel (with this information, you can use the track itself to more easily locate the front bolt holes). I repeated the same for the consoles, seat belt winders (atop the rear inner fender, in my case) and anything else secured through the carpet.
Also, if you or the previous owner has changed the color of the car and the floor is still the original color, this is a good time to paint anything that may ultimately be visible either to match the car or the carpet. Edges like where the door moldings go on or corners where the sill pieces or panels meet the carpet can have gaps and show the floor color through. My carpet is black and I found it more pleasing looking after painting these areas black, rather than the red of the body.
Once this is all done and the floor is clean, start putting down the glue on the drive tunnel and floor and on the corresponding carpet. Follow the instructions on the glue, which tell you to allow it to dry before installing the carpet. Don’t do too many sections at once because they’ll get dirty and won’t stick and you will just have to clean them and do them over. Lay in the carpet and smooth out toward the outer sills, back rise and front foot areas. Make sure any holes align properly. Check the fit of the back rise section, sill sections, etc. before you trim the floor. Use the transition from floor to vertical as the trim points. A little extra won’t hurt as you can always go back, lift the section and trim again later (this is what I keep the spray adhesive around for). Install and trim the remaining sections, with only the one over the rear shelf not glued to allow you access to your batteries. Use the lacquer thinner to clean any errant glue.
Now using your locator "map", start reinstalling the interior, seats last to give you the most maneuvering room. When opening hole for the bolts and screws, the more clear you get the hole, the easier the installation becomes. If the carpet gets into the holes, particularly with bolts, it makes it hard to get them in and you could do damage to either the floor or the carpet forcing them.
I know that does not cover everything, but that’s it in a nutshell. If your wife and/or kids are interested in your car, this is a great family project. Good luck!
Weak Spark
by W. Conrad Krist
There are many ways to check the causes of a weak spark in your ignition system. I would suggest first checking check the low tension side. Are you getting at least 12 volts from the battery and especially from the alternator? Ballasted systems are a little different and I don’t know what the voltage should be, but it should not be really low.
Check the condition of your low tension wires coming from the distributor? Check the cleanliness and quality of the connection down on the starter and back to the battery? Also check the engine ground on the left motor mount and check the battery ground (if the parking/head lights really dim when you turn the key over, you may have battery or connection problems). Low tension problems are not easy to find, but are critical. Connection and wire condition are paramount, because on a meter you might read the proper voltage, but the system can’t carry the load without breaking down.
Once you have insured that you have a good low tension side, then move to the high side, but carefully! Check the spark on all the plugs to see that they are equal. Inequality suggests the wires are bad, otherwise look to the coil hookup and the coil-distributor feed. Check the distributor cap for carbon tracks that bleed off energy.
Somewhere the total power is not getting through either as total voltage or as enough amperage. A volt-ohmmeter is essential and inexpensive, but know how to use it or you may burn it out. Check the coil and resistor without any connecting wires for their proper ohm readings. The manufacturer should be able to tell you what is a "good" reading.
Finally, make sure that the plug gap is not too wide. I had that problem where I mis-set the gap a little too wide. The car at first ran fine, but then rather quickly began to act up and be hard at starting until it would not start at all. Re-gapping the plugs made an amazing difference.
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