Topic: Compression Test
in Forum: C3 Engines
Lifetime MemberWhat is the correct way to do acompression test? Just pull one plug out at a time, engine hot or cold, throttle open or closed?? What is acceptable difference in cylinder pressure? Thanks for any advice........
I know the voices aren't real, but they have some pretty cool ideas... 
Others may well prefer a different procedure, but this is how I've always seen it done.
Both excellent advice.
If you don't pull the plugs, it can mask head gasket problems.
If the compression is low and comes up with oil added, it's leaking past the rings. If it comes up very little, it's leaking past the valves. If it's good, there is no need to do the oil test.
It is more accurate with the throttle wide open. The throttle restricts air flow and can make the average readings lower.
Be sure to crank the engine the same amount for each cylinder. If you get 4 pressure pulses on one, and six pulses on the next, the readings won't be an accurate comparison.
Lifetime Member I know the voices aren't real, but they have some pretty cool ideas...
Brian - NCM Lifetime Member
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