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MG MGB Technical - Anything to be concerned about?

I just purchased a 68 B and was checking the compression and here is what I got.
1. 150 dry 178 oil
2. 135 dry 160 oil
3. 150 dry 180 oil
4. 150 dry 178 oil

I noticed a very small amount of antifreeze along the joint between the head and block, but I can't tell if it's coming from the stat housing and blowing back, or the head gasket.
No oil in the water and no water in the oil.

Cleve Crews

The antifreeze is almost certainly from a weeping head gasket; you might save it by retorquing (hot) now. And set the valves; the difference on #2 may be valve clearance error or rust/deposits on a seat. Then drive it some and recheck comp; single time compression checks can be misleading. The rise in comp with oil may also be misleading, since the oil fills up the dish in the pistons rather than sealing the rings. The base pressure is a little low. Be sure you are checking with throttle wide open, and check/clean all battery and starting circuit cable connections - low cranking speed is a common reason for low comp results.
This is pretty common on cars that have been sitting a lot.

FRM
FR Millmore

FMR,
Thanks for the reply.
Should the compression be checked hot or cold? The numbers I provided were with a cold engine.
I'll do as you suggested and check again.
Thanks,
C
Cleve Crews

Always hot, and with the throttle wedged open and all plugs out. Could be a leaking valve, listen for a regular beat in the exhaust and intake.
PaulH Solihull

The readings are within what would be expected (10%), but if the coolant is along the head line, I would just pull the head. This is not a lot of work and you will have the piece of mind that you have a good head gasket and allow you to inspect the valves.

IMHO well worth a day of working on your B.
Bruce Cunha

I'd say that your compression readings were pretty good. The 135 is slightly low but within the 10% allowable margin. However I would expect to get 170 on a hot engine with the throttles wide open and the spark plugs removed. Regarding the weep in the cyl head I too suspect that this is a cyl head gasket leak but it is nothing really to worry about as a pellet of Stop Leak or a bottle of Barrs Leaks will soon sort that out. On the readings you have provided I can see little need to pull the head for some considerable time. Relax and enjoy.
Iain MacKintosh

I had a cracked head which caused antifreeze to appear on the block around cylinder 3 on the right hand side from memory. It was a US head and I believe they are known to crack around the air injection bosses.
Simon Jansen

This thread was discussed between 11/06/2011 and 12/06/2011

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