Couldn't fine much in a search... Have a 2k mile short block that i pulled out of a car. Started, idled and ran fine. Tested the compression last weekend (cold obviously). Piston compression tester, 3 equid pulses but the front rotor was 94ish PSI and the rear was 98ish. Motor was street-ported and built by a reputable builder 2k ago. I'll charge the battery up to make sue that that isn't skewing the results but could the motor being cold cause the lower compression than expected? Thanks in advance, Mike

 

Yes it could....but how cold was it? Was the throttle open?

 

Its a shortblock so no manifolds on a cold day (60ish degrees)...

I'm not too concerned as the car ran fine but everyone interested in purchasing the motor is asking for compression numbers. I know these numbers are still in range for a healthy motor (ie above 85 psi) but feel like these numbers are abnormally low. Thanks, Mike

 

As mentioned, the rpms will be a big part of if the numbers are decent or not. As far as a cold compression test, typically they are higher than a warm compression test.

 

I thought that the engine needed to be warm? Why would cold numbers be higher?