QuestionQUESTION: I read your proceedure on performing a dry and wet compression test on a Spitfire. It was very informative. You ended with mentioning the sure fire 100% test is with compressed air. Can you please advise me on how to do that proceedure.
Thanks
ANSWER: Hi Pat,
The process is to put each cylinder to be tested at TDC and the hand brake on and in 4th gear. You will need a fitting that screws into the spark plug hole (available from most any tool truck Snap-on, Mack, Cornwell etc.)
Plug line air into that cylinder and open the throttle and listen for any hiss and do the same at the tail pipe. Then open the radiator cap and watch for any raising of the coolant. This test will pick up any leakage so slight that there is no symptom showing YET.
A percentage leak down tester does the same thing except with it you can test rings. With just the compressed air you can't test much for rings because all engines will hiss into the crankcase, even a new engine and unless you test a lot of known condition car you can't recognize an acceptable hiss in the crankcase. For rings you should use either a leak down tester of the wet and dry test.
Howard
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QUESTION: Can't thank you enough for such a quick and detailed responce. This is my first Spitfire, growing up I was an MG guy so I am learning as I go. I have a 1977 Spitfire 1500 but don't have a manual yet. Anyway after following your instructions I have zero compression in number 2 cyl.wet and dry test. I can actually here the air passing around the valves. So the next step would be to adjust the valves. Unfortunately I don't have the specs. are the proceedure. Can you advise.
Thanks, Pat
AnswerSet the valve clearance to .010" of each valve when it's opposite valve spring is compressed. Opposite meaning #1 compressed set #8, #2 compressed set #7 etc. (you will note that two valves are compressed at a time thus you can set two different valves at a time.
Howard
