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Extract from June's Octagon Car Club Bulletin


Why does the speedo needle on my TD fluctuate wildly whilst motoring steadily? (322)

I had exactly this problem with my TF some time ago with the needle going from about 35 to 60 when gently cruising along. Eventually, after it got worse and worse, the speedo stopped registering altogether. Gripped with the fear of the sort of bill one receives for the rebuild of instruments, I removed the offending thing and dismantled it.

The inside proved to be clogged with what looked like thick grease, but was obviously oil which had found its way up the cable and over-lubricated the instrument. I carefully cleaned it all with a small water-colour brush and some petrol and the instrument has since done about 5 years service without a twitch. I didn’t even change the cable.
Norman Downie, Wantage, Oxfordshire

Roy’s fluctuating needle is an age old fault with an age old remedy. The cause is most likely to be a problem in the cable drive. This spring-steel wire wound in opposing directions drives the magnet inside the speedo. Inside the instrument this magnet pulls round a disc connected to the needle against a light spring. There are also damper springs to remove ‘needle swing’. If the cable has a dry bit, is bent inside or is badly routed it will ‘wind-up’ and then release itself every revolution. This should be dealt with by the damper spring but if it is too bad the needle will try to follow the wild differences and end up swinging about.

The cure is to remove the INNER cable and oil it thoroughly removing virtually all the oil from the top 18” or this will wind up into the speedo ‘head’ making things gooey inside and the needle very sluggish.

If this fails then ensure that the cable has nice, GENTLE curves. Any kinks will be a problem. Also inspect the inner cable. They sometimes ‘unwind’ causing a stiff spot. If necessary fit a new cable with smooth curved runs.

Handle the inner cable carefully. They have minds of their own and will leave nice black oily imprints of the windings anywhere, especially on seats, for later deposition onto summer dresses.

Use light oil not grease. Do not cross thread the knurled end fitting (easily done).

Most of this, except complete cable renewal, can be done from inside the car.

None of this applies to chronometric instruments; just the cheaper Smiths and Jaeger which Morris and BMC used.
Neil Cairns, Leighton Buzzard, Bedfordshire

The reasons why Ray Williamson’s speedo needle fluctuates are:
a. The cable is dry and requires lubrication with H.M.P. grease. Note the last 6” of the cable should be left free of grease otherwise the excess will work its way into the speedo head and really cause problems.
b. The square drive end can be worn thus interrupting the drive to the input the shaft.

The remedy is to replace.

c. The escapement mechanism is dry of lubrication and dirty. DO NOT haphazardly spray into the mechanism with substances like WD 40. The unit has to be stripped, cleaned and lubricated with clock oil. (This is difficult to explain in sketches. If Roy cares to phone me I may be able to help further.)
Ray Powell, Birchington, Kent.

Possible reasons are:-

  1. Loose or worn speedo drive on gearbox mainshaft.
  2. Worn speedo drive cable.
  3. Speedo drive cable with tight curves in fixing allowing the internal cable to snag on the outer.
  4. Too much oil in the gearbox which will ride along the inner cable into the speedo to gum up the gyro with oil.
  5. Aged speedo in need of overhaul.

One day on a long hot journey my TD speedo suddenly stuck at 50mph and then worked from 50-100mph instead of 0-100mph!!
I found that the problem was oil ingress from the gearbox to the drive cable.
All was well after cleaning the speedo in methylated spirits and reducing the oil in the gearbox to “half” full.
John Beavan, Bartestree, Worcester.

Old cars which haven’t been on the road for many years always seem to have a speedometer which is stuck up with ancient grease and oil. All the components are there, it just needs a thorough cleaning/degreasing. With what should one clean the works of these delicate instruments? Should they be lubricated at all, and if so with what? (323)

Ideally, (as with watches and clocks) the mechanism should be totally dismantled. However, the grease can be effectively removed by fully submerged overnight soaking in a clock cleaning liquid such as ‘Horolene’, and through rinsing. Use of an ultrasonic cleaning bath would enhance and speed up the process. Dry off carefully (hair dryer) and lubricate with clock oil. Other oils will not do as they tend to be corrosive to these delicate components. The oil can be applied sparingly in tiny droplets from a pin or piece of fuse wire to fill the bearing sinks (small recesses around the bearing holes) and to all moving parts except the gears which, as in all horological usage, are designed to mesh dry. If this fails; spray the whole xxxxx lot with WD40 and/or pack off to specialist restorers! I can assist in procuring cleaner and oil if locally unavailable.
Martin Moore, Birmingham

Do I need to remove the cell tops and battery leads when trickle charging? (322)

I never remove the cell tops as they have vent holes.

It’s also quite O.K. to leave the battery connected due to the fact that ‘our’ charging systems have a cut-out fitted. I usually connect the charger to the +ve lead of the battery and the -ve lead to any metallic part of the car. Note: this only applies to vehicles with a DYNAMO. If you have converted to an ALTERNATOR (some owners have) then both leads must be removed or the diodes will be ‘blown’.
Ray Powell, Birchington, Kent

No - sufficient ventilation is provided to cope with gas emission during charging or it would not perform in the vehicle.

However, the only true way to check the charge efficiency is to measure the specific gravity of the acid using a hydrometer. Removal of the cell cap makes this job easier!
Arthur Skinner, Loughton, Essex

Can anyone tell me where I can obtain the screws which hold the windscreen frames to the central support of my 1930 M-type?
They are raised head countersunk chromed brass with a 5/32 Whitworth thread. I believe 3BA is a very similar thread but equally unobtainable.
(No 322)

Some are certainly available in Helsingborg, Sweden, Bjarne Bergengren with his customary generosity has sent Sam a dozen (MT)

Why do the water jacket side plates corrode so quickly on my P type? It is just that they are made of poor quality steel or are they acting as ‘sacrificial anodes’? What are sacrificial anodes anyway? What is the difference between the various antifreeze/corrosion inhibitors on the market, and should I be using something other than MotorWorld’s cheapest? (Nos 307 & 320)

Sacrificial Anodes. Put simply if you connect two pieces of dissimilar metals (e.g Aluminium and steel, zinc and copper) by bolting, welding or by a wire which is an electrical conductor and then put them into a liquid which will conduct electricity (e.g. water, salt solution etc. but not petrol or oil etc) then the more active one becomes an anode and corrodes away (is scarified) whilst the less active cathode is protected. So, in the examples given aluminium becomes an anode to steel and zinc an anode to copper.

If a piece of zinc, aluminium or magnesium is connected to the steel hull of a boat the steel is protected from corrosion by the more active aluminium, zinc or magnesium, which are replaced every two or three years.

On your engine, if the side plates are made of steel and the block is cast iron then the plates must be anodic to the block. They will corrode sacrificially (often quite severely at the junction) but will protect the block for a short distance. Corrosion is prevented by the inhibitors in the antifreeze which are used up slowly so you need to replace the antifreeze every two to three years (two if you have an alloy head) and the solution must be kept to the correct strength. Do not top up with water alone. I always use the well known brands or others which conform to the Britsh Standard.
D. Fletcher, Banbury, Oxon

Reading Neil Cairn’s (No314) and Peter Seymour’s (No319) articles on the development of MG engines made me wonder just how similar are the blocks on the XPJM and XPAG engines. It is possible, for example, to bore out the 1140cc Morris to the 1250cc XPAG size? (No 321)

Anyone who was at the MGCC Abingdon Beaulieu Weekend’ last year will have seen a cylinder block “Bored to standard” for sale. It had the casting number 24144 on it which told me that it was in fact an overbored 1140cc XPJM/XPJW block. There was not an MG cast-in motif as on the casting number 24146 XPAG block. The later SC2/TD2/TF block is casting number 24445, again without the MG motif. So the answer to the question must be YES you can bore out a 1140 to a 1250. The difference is only 3mm. A lot of Morris and Wolseley blocks appear on MG cars, even once bored out to +0.040” oversize they can be sleeved back to 1140 to 1250 sizes.

MY Question is: if the 4/44 ran alongside the TF1500 and both used the same block can a 4/44 be bored out to 1466cc?
Neil Cairns, Leighton Buzzard, Bedfordshire.
(A longer article on this subject (by Jake Wilson) will follow in a later issue - MT)

Can any member advise me of a good, long lasting, very high temperature resistant finish for cast iron exhaust manifolds? I understand that powder coat finishes will not stand up to the demands required. (No 311)

I have seen a manifold which has been sprayed with TEFLON, the staff used on oven pans. It looked good but I don’t know how long it lasts.
Neil Cairns, Leighton Buzzard, Bedfordshire.

Does anyone know of a source of leather washers for footpumps? I have had little success with botch repairs on my ‘Kismet Popular’, but it is too beautiful a device to replace with a modern plastic and tin pump. (Nos 306 & 319)

I have recently repaired an old ‘Long Tube’ type hand pump with the modified system shown below:

The brass piston is machined to a suitable diameter less than that of the pump barrel to allow air to pass on the upward stroke as the O-ring stays at the bottom.

On the downward stroke the O-ring rises and makes the seal. If Chris is still having difficulty finding a leather washer I would be pleased to make a similar part for him.
John Askew, Beaumaris, Isle of Anglesey.

I have repaired several of these pumps by making new leather washers. If Chris wishes to contact me I will discuss options with him.
Terry Andrews, Sidcup, Kent.

What are the best places to use when jacking up a MMM car? These days garages and the like seem quite cavalier when jacking a modern car, using the middle of axles etc., but I am always worried that this might bend something on an old MG (No 306)

Try using the chassis rails.
Terry Andrews, Sidcup, Kent.

Having installed a lubrication system to my PB (0360) as per Barry Walker’s drawings I find that some of the feed plugs are open and that some are adjustable for the feeds. Can anyone tell me the sequence of adjusting the feeds to give the correct amount of oil? (Nos 306 & 319)

First you will need a good quality grease gun for the oil, the only one that is up to the job is a WANNER.

  1. Close all the needle valves. The rear spring ones should not have any needle valves. Pump the oil up to the rear springs.
  2. Go to the next furthest needle valve and open one turn. Pump oil until that item is fully lubricated. Then shut the needle valve and move onto the next nearest and so on until all have been fully lubricated for the first time.
  3. With all needle valves shut off, start at one nearest the lubricating nipple and open 1/4 of a turn. Go the the next nearest and open 1/2 turn. As you move away from the lubricating nipple increase by a 1/4 turn of a turn each time. This should set up the lubricating system so that each component gets its fair share of oil.
Terry Andrews, Sidcup, Kent.

Has anyone a genuine original M-type toe-board (the one the pedals come through or upon which the passenger’s feet rest) from which I can get an outline in order to make a copy? (No322)

I have in my possession (and i know that I am far from alone in this respect) a copy of the Works drawing of the body work of the ‘M’ type. To be precise it is for a 12/12 but it is basically the same thing. This shows the outline of the toe board but it is not to scale. If this is of any help please let me know.
Norman Silk, Heswall, Wirral

I am restoring a T-type. The car has stood idle for some 20 years and will be a few more yet before she is taken on the roads.
Should I use the existing tyres?

As garden ornaments perhaps but not on the road.

Tyres die of old age not just tread wear. Having decided that the inner tubes need replacing, despite being stored within the tyres, how can you expect the tyres themselves to have survived the effects of exposure to ultra violet light and who knows what else over the last two decades?

The most sensible solution would be to leave the car on its existing tyres during the restoration and then buy a complete new set (including the spare) when ready for the road.
Dave Whitfield, Stafford.

There is wear in the King Pin bore in the axle beam of my MG Can anyone suggest a method of repair. (323)

The simplest way to get of the play in the king pin bore of your axle if you have limited mechanical resources and don’t want to disturb the originality, is to heat the axle-end with an acetylene-oxygen torch to a dark orange glow, and then make the bore narrower by hammering it carefully on the outside (Strike while the iron is hot!) from all possible directions radically until it is small enough to ream to its original dimension. You may have to reheat the axle in the process. But let it cool off gradually by itself. Then borrow an adjustable precision reamer like the one you use for reaming the king pin bushes, but be careful not to over-ream, because the new king pin should be a snug fit, because the cotter pin alone can’t do the job of keeping it in place. With the bushes, on the other hand you are supposed to leave a minimal play to make room for the grease.

The alternative to the above, is to install an oversize king pin, but then you can’t use the original spare, ever. And you have to have the kingpin made. I have done this job both ways, but I know which way I prefer.

There is of course also the possibility of boring out the axle and installing a steel bush, but the axle end will get thinner in the process, and you have to take the axle to a machine-shop.
Bjarne Bergengren, Helsinborg, Sweden.

We can still obtain unleaded fuel here but who knows what the position will be in three or more years? I am therefore looking to change the cylinder heads on my MG TD and MGB to run on unleaded fuel. I am concerned about the effect of this fuel, which contains a lot of aromatic hydrocarbons, on the organic seals, membranes and gaskets especially in the fuel pump and SU carburettors. I have heard that damage to these parts could cause a fire. Can anyone confirm this?
What can be done to avoid this

I have been running my TB, with no alterations, on unleaded fuel from the moment it came on the market, and later my TC too, without any problems whatsoever. I am driving my T-type about 5000 miles a year, and have done so for the last 23 years.

I will admit, that I have on my shelf a modified XPAG cylinder head with hard valve seats, just in case. Up to now, it hasn’t been necessary to use it, however.
Bjarne Bergengren, Helsingborg, Sweden

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