'73 911 E compression test

[tmctguer]

i have a '73 911E with 2.4L MFI. the engine has approx. 60,000 miles on it. i did a compression test and here are my results:

cyl. 1: 142
cyl. 2: 155
cyl. 3: 150
cyl. 4: 155
cyl. 5: 153
cyl. 6: 155

how do these results look? should i be worried about the low reading of #1 cylinder?

[Early_S_Man]

Those figures are just fine for an engine with 8.0:1 compression, yielding a mean of 151.7 psi. No, don't worry about #1, as it is only 10.3 psi from the mean figure.

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Warren Hall
1973 911S Targa

[True Brit]

I did a similar test on my '73 2.4E, which yielded about 125-130psi on each cylinder. However (a) the engine has covered about 100,000 miles (b)I did it cold, which I probably shouldn't have done, and (c) an "expert" told me that a compression test is fairly irrelevant on a 911....but I don't know why. Anyway I only carried it out to make myself happy that the engine was "generally" sound.

[tmctguer]

so a ready of 142 isn't a sign of something like a loose or broken head stud?

[Don in Redondo]

I agree with Warren that you have nothing to worry about, although I am would very surprised that you are getting compression readings of over 150 psi with 8.0-1 pistons, I would expect 9.8-1 piston setups, which may mean that you have a rebuilt piston/cylinder upgrade, and the need to run higher octain fuel.

[tmctguer]

i just put a tank of 87 octane fuel and it runs fine.

as far as the compression results go, i duplicated the test to confirm the readings of each piston and they came out almost identical on both tests.