QuestionHi Howard,
I did a couple of tests on my 77 spitfire 1500. came out at 115 to 120 each cylinder. The car runs really well now, but should i worry about the numbers? I do have some blowby, but it still runs very well.
I had heard that some spits have a low compression engine. should mine?
It was a catalytic car, but now all is removed. Seems to have more than enough power, and plugs looks just right-
Ps where shoud timing be set with a new weber 32/36- have found some different answers-
Thanks so much
Chris Runnels
AnswerHi Chris,
With only a 5 lb difference in the readings I would not worry too much about the low over all readings. That could be a gauge problem or just low compression which many 70's cars did have. (7.5 to 1) noted in the engine number with an "L". This car needs low octane gas too.
I would run a "Wet" compression test to see how much blow by you do have. Just run a normal compression test (throttle wide open) and then squirt a few shots of engine oil into each cylinder (about a teaspoon of oil) and run the compression test again (throttle open).
If the Wet test is more then 10% to 15% higher then standard compression test, you do have excessive blow-by due to a ring problem.
If you do have the low compression engine ("L" in the eng no.) and you have been using high octane gas, this will cause the engine temp to run high and burn a lot of oil due to the "Excessively slow burn of high octane fuel" This tends to burn a lot of the oil off of the cylinder walls on the power stroke.
Howard
