Well I have been a member of this community for a very long time. I have been through about 5 different setups on my car and am no novice when it comes to building cars. I have ran into a problem that has me and all of my good friends/techs stumped. Im running a built 420a turbo. I recently assembled the engine. Prior to start up I did a compression check just to assure myself due to some prior bad luck. I got 155psi across the board, the rings were definitely not seated but the consistency was on point. The car started up wonderfully and ran great. I shut the car off to do an oil change after it reached operating temperature. I cranked the car after changing the oil and it sounded like a cylinder was down. I shut the car off and did a hot compression test. cylinder one had nothing, cylinder 2 had 75, cylinder 3 and 4 had 175. At this point I was ready to jump head first off a cliff. I pulled the v/c off and yanked the lifters out to ensure the valves were seated. I pressurized cylinder 1 and 2 to 100 psi regulated. I then used a stethoscope to listen inside the intake foor an air leak, got nothing. I pulled the turbo manifold off, nothing. The cylinders were holding pressure fine. I bled the lifters down completely and re assembled the head. I compression tested the motor with the lifters bled down. I got 175 across the board. I started the car and it ran great. I shut the car off feeling great. The next day I got to the shop and cranked the car. The same problem returned. I figured the the lifters were getting "over pumped" or stuck fully extended.. I replaced them with a brand new set of 2.4l lifters. same problem. I am at a complete loss right now. Has anyone ran into this before? All the valves are ss 1mm oversize valves and the head just left the machine shop!

the setup:
420a
crower 2 na cams, springs and retainers
pt lifters and rockers
ss 1mm oversized valves
je pistons, crower rods, mellings oil pump
arp everthing
amm intake manifold and exhaust manifold
precision pte 6766 turbo
ms1 v3.0
Injector dynamics 1000CC injectors
lots more but you guys get the point

So, an intermittent loss of compression?

Originally posted by eclipse982nrRST
So, an intermittent loss of compression?

It was a complete loss of compression only after the lifters pumped up. I put new pt lifters and 2.7 rockers arms in just in case and re tested the car, same problem. I went to a u pull it on sunday and pulled a set up stock cams in desperation. I threw them in and voila, the car was running great besides needing some changes to the idle on ms. The resting portion of the crower 2 cam lobes on cylinder 1 and some on 2 were oversized causing the valves to hang open. Im going to call crower in a few to see if they will stand up to their name.

Yes, I was going to tell you it had to be a valve seating issue. Good job though. Good luck.

Interesting read. Thanks for reporting back. Curious to see how crower responds.