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Discussion in 'Technical Q&A' started by jakermc, Jan 21, 2004.
'95 F355 GTS:
Any reason to worrow about the 185?
Maybe. Question, was the engine good and warmed up (full normal operating temperature*) at the time of the compression check? If so, then cylinder 2 is marginal. If not, have it redone with the engine good and warmed up.
*You might consider a nice romp through your favorite back road to blow the carbon out before arriving at the mechanic to check the compression.
This is for a car I am looking at buying. The test was done by the Ferrari dealership. I always understood that the variance between cylinders was more important than the absolute number. Is the same true here? What are the rules of thumb I should go by?
I've always been told a 5 - 10% range is within the bounds of being reasonable. 185 to 205 is therefore at the limit of this. To Mitch's point, ask what the car's temp gauge read when they did the test (again, I'd look for 185 degrees or so).
Why not tell them you are a bit surprised and ask for a leakdown test (again, on a warm engine)? This will educate you (and the dealer) as to whether there's a problem [e.g., if most cylinders are 4 - 7% and one is 12% or higher] and they should be able to tell you the source of the issue (valves, rings etc) by listening for the source of the escaping air.
The leakdown test (especially on the '95) is more critical than the compression test, although both are prudent. It will alert you of the 'valve guide issue' i.e. compressed air is inserted into each cylinder and 'leaking' from the valves is measured in percentages. Leakage over 10 percent is generally accepted as problematic. All independant F dealers are aware of this test and it should be done before purchasing any 355. The first 2 355's I looked at ('97s) both failed the leakdown, which is why I went with a '98. Best of luck.