Should a person have air passing exhaust valves when 20 psi is on the engine checking the boost with an air compressor, is their a spot in the firing cycle that all valves would be closed? I remember once talking to a guy at a diesel shop that told me I should have no air movment past the valves but to me that was a near impossible statment unless I am not thinking clear. Chaasing some possible bosst leaks....... again

J

 

Th answer is no.Only one cylinder at a time will have the valves closed on the compression and power stroke.

 

At no point should there be both intake and exhaust open...

(I pretty sure about that...)

If you want to test the therory... Roll the crank to a new position and re-test.