Compression Test Confused!?

tombardier said:

Wet test is the only way to prove that. Also, if you have got dodgy valves then that could mean that your compression gauge is fine. Nothing so far is proving that the gauge is knackered surely?

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Thank you. I will try a wet test tomorrow night to see if it makes any difference. Obviously, if my valves are goosed it won't hold pressure in the cylinder but I am fairly certain that the gauge should maintain its reading rather than drop back down to zero? Do they work off reading pressure buildup which is contained within a chamber within the gauge its self (and held in place via a small poppet valve) or does it simply go on the pressure in the cylinder at any given time? If the gauge is right, then when the piston reaches TDC on each cylinder, one or more valves must be slightly open to the extent that the cylinder will only reach 220PSI before it is allowed to escape. The only thing that I can think of which would cause this is the cam being out a tooth or two... or three

-Tom

if proper guage it has a one way valve which you release to let pressure off that way it measures highest pressure achieved over several turns of engine ,why time it takes to reach pressure is helpful ,if it dosent seal highest true pressure wont be reached as pressure is lost on down stroke,but not as much as gained on upstroke ,so id think a good guage would show better pressure

jamesmartin said:

if proper guage it has a one way valve which you release to let pressure off that way it measures highest pressure achieved over several turns of engine ,why time it takes to reach pressure is helpful ,if it dosent seal highest true pressure wont be reached as pressure is lost on down stroke,but not as much as gained on upstroke ,so id think a good guage would show better pressure

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Alright thanks. I'll leak test it (it's the only other bit of equipment that I have access to which I know is reliable) and then I'll get back to you with the results.

-Tom