Experience Dealership line mechanic on MG, Triumph, Jaguar for 15 years, Instructor in commercial mechanics school 2 yr. Product information manager for piston and valve manufacture, Instructor & hotline answer man for import car parts importer 15 yrs.
Organizations Associate member SAE
EAA member
Publications Import Car magazine
Education/Credentials ASE Master Auto with L-1 certification up to 2000
Question Hi Howard, I see that the TR 3 is not in your listing of
expertise, but hopefully you can guide me on this question.
I'm looking to potentially buy a TR 3 and the compression
readings are all in the 196-198 range. Seems awfully
high to me, is this high pressure correct?
thanks in advance! regards,
Joe D'Amico
Answer Hi Joe,
I do have some experience with the TR-3 and I agree, those readings are too high. This could only be if an engine was heavily carboned up or someone raised the compression ratio way high. As I remember, the TR-3 had a compression ratio of 8.5 to 1 and that should not get a reading of 190+ on a compression test even with great rings.
Did you run that test or are you being told that? Was that a dry test or a wet test?
What is the oil pressure at cold start up and how quick does it come up? And how slow does it go down when the engine shuts off? Then run the engine until the oil is up to operating temp (longer than coolant temp) Then repeat the same tests. What is the oil pressure at idle and at fast idle, how fast did it come up and how slow does it go down. Oil pressure has nothing to do with compression tests but it is a indication of engine condition. I would expect to see 35 to 50 PSI at idle with hot oil and 60 to 80 PSI at fast idle hot oil on an engine that was in good condition with 10w 30 fresh oil or 20w 40 in warm climates.
However, if I seen a TR-3 with 15 PSI at idle and 35 or 40 PSI at fast idle and a 190+ compression test, I would suspect a heavy amount of carbon in the combustion chambers. Or a head that had been resurfaced too many times.
Two things would happen, one the starter would have a hard time turning it over and two, it may have detonation even with high test gas.
That is my guess form what you tell me. Proceed carefully.
Howard
