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Extract from October's Octagon Car Club Bulletin

Technical Torque

Yet more apologies. It appears to be computer translation problems again. In Jake Wilson's 'A box of Neutrals' part 2 on page 19 of the August issue the dimensions of the bar of steel should have been 1.5" square whilst the dowel (page 20) was 6.5" by 0.5". It appears that the Editor's computer doesn't like the way my PC handles fractions.
No questions this month. I can't believe that all members have solved all their problems. If you have any questions, or any answers, tip or comments please write to: Malcolm Taylor, Whisket Green, 56 Daisy Lea Lane, Huddersfield, HD3 3LL.


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? (320)

I have recently been informed, from what should be a reliable source, that the corrosion inhibitors in 'old' conventional ethylene glycol antifreezes are responsible for a significant proportion of cylinder head gasket failures.
Apparently, the answer lies in using one of the pre-mixed Trigard-based 'long life' products such as Bluecol Protex, Unipart Super Plus, Batoyle Masterfrost. Apparently these will last for four years, twice as long as the 'safe' life of ethylene glycol products.
I am not technically qualified to comment on this information but I do wonder whether this may provide a clue to the corrosion of the side plates.
Neville Mantle, Wetherby, West Yorkshire.

Following this article, the Business Manager of Trigard Coolants has clarified the situation

My TC appears to be fairly well tuned but, when 'freewheeling' down hill in gear, the engine backfires. What is the cause of this and how can I rectify it?

I have usually found that a small exhaust leak in the pipe run before the silencer results in backfiring on the overrun. Failure to cure the fault usually results in a split silencer or the end of the plate blown out.
Modern cars do not seem to have this fault. It could be something to do with better control of the fuel mixture; also some systems have a cut off valve (for fuel economy) when on the overrun.
I have noticed that modern silencers are crimped along the full length of the folded seam (presumably for greater strength) they didn't used to be.
J B Proud, Orford, Warrington.

Does anyone know how to make the windscreen on the TC fold easily? Is a thin washer required between the screen scuttle bracket (lower stud) and the screen stanchion?
Does the upper part of the screen scuttle bracket have to be bent (in a vice)?(327)

To allow for ease of folding firstly slide the "D" Washer onto the pivot stud followed by the half nut and finger tighten this nut to pinch the "D" washer, then release this nut by half a turn. Fit the domed nut and tighten against the half nut making sure that you do not close the gap created. This should allow the windscreen to pivot smoothly from upright to full flat and back again. Some drag will be caused by the rubber weather strip. This can be relieved by reducing the width of the strip. Finally, fit the cone and lock the windscreen in place with the wing nut. There should not be any need to bend or modify the scuttle brackets to achieve the above.
John Beavan, Bartestree, Hereford

Many members will have the late Don Jackson's excellent booklet "Your SU Companion".
In this, Don advises that the factory recommended caburettor needles gave an unduly rich mixture and he suggested using a weaker alternative, (not the factory recommended "weaker" needle). As an example he suggests, for an engine in standard tune, using an EU instead of an ES in TCs and TDs. Unfortunately, there is no recommendation for a YB. Can anyone help and let me know what the equivalent of the EU is, bearing in mind that the factory standard needle for the YB is FI. (325)

I would like to thank those members who have been kind enough to supply 'Answers' to my questions. in addition to what has been published in the Bulletin so far I have also received (courtesy of Tony Hebdon) a full set of SU carburettor needle profiles. Following a 'wet towel' evening I decided that a DZ needle was the nearest I could find which equated similar differences to the standard needle to those Don Jackson had recommended for the TC's and TD's. Since fitting this needle my petrol consumption has improved to approximately 32.5 mpg (previously 28.5mpg). The car seems to be pulling equally well and the plugs seem to indicate the correct mixture.
Peter Arnell, Dorking, Surrey

I thank Mike Smye for his interesting answer(no 326) to my original question (No 323) on the Y type engine. I still wonder, however, why plugs are of short or long reach. Is it simply to avoid being thumped by the top of a piston? (327)

After World War 2 fuels improved, compression ratios rose as did the power output of engines. The engines ran hotter and the need to keep the exhaust valve seats cool was important. So, cylinder heads became a bit thicker as the waterways were made wider to let the, now pumped water around the valve seats. Plugs also suffered and as an aside they too gained a much larger surface area to get rid of the heat into the head. This was done by making the water jacket surround the plug and by making the thread longer. If you look at old side-valve heads there is quite a large area around the plug hole with no water jacket. Now, look at the SC2 or TD2 cylinder heads and you can see the area is thicker with a water jacket underneath. This was not peculiar to MG. All car engines were going over to long reach plugs, the name 'Long Reach' being given to plugs with the long thread, about 3/4". The 'Short Reach' plug had about 1/2" thread length.
This fits nicely into the modification of the improved water flow of the 'round water hole' heads and blocks, as it is this later head which is the 'long reach'. It has to be remembered that the XPAG was a pre-war design, an enlarged Morris 10/4 engine.
Short reach plugs were the norm then, around 1935. By 1951-ish when the SC2/TD2 engines came there had been 16 years of technical development in engines to satisfy war needs, The 'A' and 'B' series engines designed after the war, both had long reach plugs from the first engines. (Austin A30 and MGZ Magnette)
As Miles says it was common for people to put in long reach plugs to try to improve the compression ratio a little (especially in small four stroke single cylinder motorbikes!) The danger here is of the piston hitting the plug or of a valve hitting it if it is a hemi-head. A short reach plug will work in a long reach head but the spark will be masked and the power reduced.
So the answer here is that the metal bit the plug screws into was made thicker to allow the heat to be dumped (i.e. a heat soak) and to allow water round more of the cylinder head combustion chamber. The length of the reach does not affect the plug's heat rating, this is controlled by the length of the insulator inside the plug. Or have I opened up another query here?
Neil Cairns, Leighton Buzzard, Bedfordshire.

Tips and Comments

Keep your equipment in good order
Have you notice recently how the rolled hide insters in your wire wheel hammer quickly curl up and disintergrate after just a few wheel removing exercises?
The narrow rounded edge of the wheel nut ear obviously causes this and it dosen't take much imagination to realise the dire consequences which may result from using a hammer in this condition if it slips off the target. Bent spokes, a dent in the wing, instant paint removal; I was more fortunate, just grazed knuckes!
I purchased two new inserts and, after drilling out the old and squeezing in the replacements I fitted a ring of thick-walled copper tube 1,5" inside diameter and 3/8" of the insert exposed.
This does really hold everything together and when wear eventually takes place simply hacksaw off the residue, remove the copper ring and start afresh so doubling the life of the hammer.
Tony Whitmill, Kettering, Northants

I have been very enthusiastic about Jonathan Taylor's steering tip in Bulletin No 320. A friend, engineer and MGA owner Fritz Remiger has made a "Panhard rod" for my TC.
The effect is really as Jonthan described!
The car has very smooth steering. All the nervous reactions I used to to have to balance have gone - it feels almost like power steering, Fritz also made a rod for Gunter Thielmann's TC. He confirms my feelings and is also very happy with his smooth TC steering.
Walter Prechsl, Obersulm, Germany
(Walter may produce more of these rods if there is interest, Watch for member's advertisments or contact me - MT)

Crankshafts, Blowers and things
Earlier in the year my ND went back on the road after breaking its crankshaft in France. When it was dismantled the crack was through the web between the front main bearing and No1 journal. It appears that the loading from the belts driving the side mounted Marshall 87 blower had been putting too much load on the front of the crankshaft causing it to break. The front of the crank is unsupported beyond the front main bearing altough the drive gears will restrain it a little.
It is suggested therefore, that when belt driven blowers are used the belts are not tightened too much thus causing excess load on the crank. The belts need to be tight enough to drive the blower without slipping at high revs. Modern notched fan belts are designed to be more flexible around pulleys and, although they don't look period, are proably a better item and less liable to slip.
We have also fitted an additional outrigger bearing (a la J2) to take the loading from the belts on the ND.
Another point to remember on supercharged cars is to limit the distributor advance to 6°, (usually 12° on unsupercharged cars. I had mine altered by Norman Cousins of Maidenhead (01628 819071). This allows the engine to rev better at higher speeds.
Norman also deals with SU fuel pumps, cut-outs and other electrical parts. He told me that pumps which have been unused for over a year can fail to work next time the car is wanted because petrol has evaporated in the pump leaving a sticky residue which gums up the one-way valve disc. These should be taken out, cleaned and replaced.
Phillip Bayne-Powell, Normany, Surrey

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