+ 1

Bent intake pushrod, or intake rocker backed off can still show a good leak number but no comp 'cause the valve's not opening to let any air in. A really flat cam lobe will do the same..

ya i dont know much yet.... but it didnt sound right to me eather. with only 5psi that is like a dead cylinder witch can be the ression for the oil presher and gas smell with it not fireing and gas dumping in to the oil. but i never heard knocking or any thing and seamed like they both where running good. now it is hard for me to tell right now whats running good and whats not. went from a single 454 to twin 500 hp efis. when i was only able to get 50/55 out of my 27 to running top/only once but it was 82. 70s all day.

a bent rod is one of the things he sead might be the problem.

Good point,,,, I didnt think of that sernario

that makes sence but i would think the owner ,or his mechanic would hear the noise from the xtra clearance,unless the rocker is not moving at all.

where i have the work being done i dropped it off after the final pull out and had them winterize it this time and they didn't hear any thing at that time ether. and like i sad be for 500 efis sound a lot better then my 454. even on 7 instead of 8.

Broken top piston ring could also have good leakdown #s

also if I remember correctly a broken valve spring once gave us a good leakdown # but very low comp readings. putting the 100 psi air into the cylinder closed the valve against the seat.

Also other factors that can give you good leakdown #'s is high valve spring pressure's when in fact a problem can be taking place in that area.

I would like to hear more about the negitives of leakdown testers. Neither comp test nor leakdown down tests are 100 % full proof. I know alot of people live by a comp test along with a lot of people live by leakdown testing.

IMO both are helpful for testing and I would do both but neither are a 100 % for problem solving. So far some really good points up here. thanks

this is some good reading and advice im having both test done leak down and compression
thanks for all advice will post results

+1
If there is no air gettting into the cylinder you will not get any compression readings, but leak down will be fine. You will not hear much difference in the way it runs either, other than it won't have the power that it use to have. I've seen this many times and has always been due to bent push rod or loose rocker. Your mechanic will find it most likely by pulling the valve covers, and the good news is that it's an easy fix.
Good luck!