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compression question

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ahpook

ahpook

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Nice day sunday, so I decided to play with the 79. Checked the compression, just to play with my new tester. ARGH! Cylinders 1-3 were around 100-110, but cylinder 4 was stuck at 60 psi. Put in a little oil, got it up to 100. My question is, do you check compression with the engine warmed up, or is a cold
(50F) check accurate?
 
Warm, by all means. All the bits need to be at, or near to operating temperature to insure that proper expansion has mated the surfaces, etc. Pistons and rings aren't even round when they are cold.
Warm it up and see if things improve.
Jeff
 
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