MG-Cars.net

Welcome to our resource for MG Car Information.

Recommendations

Parts

MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG TD TF 1500 - Compression

The head on my TF 1500 has been shaved too many times. The engine is on the edge of pinging (detonation), even with premium fuel and static ignition timing set at TDC. octane booster helps, but it is expensive and a hassle to fiddle with. The engine was recently overhauled.

From interpolating stage tuning data, the compression ratio is 9.6. Compression readings are between 175 and 180 psi on each cylinder.

I would like to reduce the compression ratio to 9.0. According to my calculations, a .085 inch head gasket (compressed) will do the job. Gasket Works in California makes copper head gaskets that are the required thickness.

Does anyone have experience with thick copper head gaskets? I am told that they tend to leak unless special precautions are taken. What are those precautions? Would it be better to use two thin copper gaskets with a steel insert in the middle?

There are other options like shaved pistons or porting/relieving. Are these choices better?

Thanks,

Ben Prince
Ben Prince

Hi Ben, In have a similar problem with the TD. I get around it by using about 10% avgas with premium fuel. If you have easy access to it this may be worth a try.
I had a sprite years ago that needed to have a reduction in compression. I was young and hard up for cash so I fitted 2 head gaskets. This is not recommended by all the experts, but it was very successful. I would try a thicker head gasket if you can get one. It can't do any damage.
cheers,
Paul.
Paul van Gool

I have a TD XPAG milled to at least 9.3 and I think it is more like 9.5 and run standard 89/90 octane. No problems or ping, or bang, or detonation. With this small a bore there should be nothing wrong with the 9.6. Did the outfit doing the milling properly debure, relieve sharp edges and high spots according to the special tuning manuels? Years ago, I ran this engine with both an annealed copper and soft alluminum gaskets to futher raise the CR. I think we got it up to 10.5 or 11 CR with the allumunim gasket. We used the old 95 high test in it with no problems.
Blake J.

You may need to grind off spots in the combustion chamber as indicated in the stage II tuning ( see the Special Tuning Manual or othe books which include the Special Tuning Data).
My TF 1500 is Stage II tuned ( 9.5 comp ratio) and I have no pinging.
You may need to retard your timing a bit until pinging stops. If this doesn't work, grind off the sharp edges in the combustion chamber as per Special Tuning.
Don Harmer

This thread was discussed between 18/06/2000 and 21/06/2000

MG TD TF 1500 index

This thread is from the archive. The Live MG TD TF 1500 BBS is active now.