When my car was tuned at DB Performance not too long ago we noticed it was down on power compared to similarly modified cars. Did a boost leak test, results were 160-170-160-135 at the time. Went in a while later to do a leakdown test, compression was 163-180-165-140 with leakage being 18%, 3%, 12%, 52%. We clearly heard air escaping out the exhaust on 1, 2 and 4, with 4 actually being heard in the exhaust manifold and turbo. No air leaking anywhere else.

I know there are a lot of variables, but my car isn't modified all that much, my cams aren't wild at all (HKS something or other, long story...), the valvetrain is all in place and the car runs great otherwise. It gets autocrossed regularly in the summer, so the only thing I can guess is that either there is carbon build up or the revving damaged the valves.

Obviously, worst case is the head gets rebuilt, but I'm kind of hoping that someone has experienced this and what they discovered. I did search but couldn't find anything.

 

if the test was done properly you need a "valve job". 18% is too much leakdown and forget about 52%. It sounds like you have seating issues on the exhaust side.

 

Was the leakdown test done with the cams in the car?
Do you have a cam gear? If yes, was it set to zero?

 

I will answer for Matt:
The test was done with the cams in the car and he does not have adjustable cam gears.

 

Correct. I'm weighing my options (if any) before I go ahead with having head work done. I wasn't sure if it would be worth using anything like Sea Foam to try and correct the problem before throwing in the towel, or if that would just cause more problems.

 

Make sure you have the lifters checked. There have been situations where they do not have full range of motion and hold the valve open.

 

The lifters were bled when we put the cams in, makes sense if they pumped themselves up too much. Thanks for the info.

 

Sea foam will not help the problem. You need to do a valve train job. I have a similar problem in #3 cyl. 80 psi in the cyl and it leaked down to almost 70 psi. I also have 3 leaky cylinder valve guides thanks to a A@@Clown that was suposed to know what he was doing. Best advise is to redo valve train the parts are not that expensive to buy if you do it in segments.

 

Fair enough. Do it right or don't do it at all.