QuestionQUESTION: I recently bought a 1961 MGA and last night I did a compression test. The car has been sitting for several month as I've been working on it.
Cold the cylinders read 139/118/138/139, wet they read 163/138/162/163.
I could not do a warn test..I've had the gas tank off and have pretty much removed most of the wiring.
Question I have is how can I tell if the issue is a broken ring or a value issue with out pulling # 2 piston?
The head is from an early B, so I'm tyring to determine if it's a head or ring issue.
ANSWER: Hi Dan. Remove #2 spark plug and pour 2 teaspoons of thin oil into the hole. Do the compression test again immediately. If the compression comes up to 160 then you have a problem with the rings. If the compression stays around 120 then it is a faulty valve.
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QUESTION: The compression came up to 160, so I have a single cylinder with a ring problem.
I'm going to have the engine out soon and based on the compression I have in the other cylinders, should I just check the bore and buy a rings set and replace all of them at the same time? I believe the engine has been rebuilt - so All I really want to do is replace parts... oil pump, water pump, gaskets and general clean up.
If it needs to be machined, I may bite the bullet and move to a MGB 3 main.
Any problem with that approach?
AnswerHi Dan, Your approach is sound, but before you strip anything, I would run the engine for a while and re-do the compression test. Sometimes a ring will stick in the piston, and a bit of use will free it up.
If you do strip the engine, it would be a good idea to inspect wearing items, including main and big end bearings, and also to take out the cam followers and inspect the camshaft lobes. Other low-cost replacement items would include the timing chain.
