30 PSI compression after rebuild help!

B

Brad406

Greenie N00B Member
I have a 07 CX7. I have taken the engine out and rebuilt it. New pistons rings, new VVT sprocket, new head gasket, new crank shaft position sensor. Time the engine, the valves were straight so cleaned them up. Did a compression test and I am getting 30 to 33 psi on 3 cylinders and 1 cylinder is reading nothing!! I made sure the timing was correct with the timing tool and the bolt to make sure it was at TDC. Even put a bolt in the crank shaft pully when tight it down so it didn't move!

This is not my first time rebuilding an engine but first time having this situation! I am totally lost on what could be causing this.

Help before I start putting dents in the car!
 
How did you deal with lash on the valves?
 
Easter Bunny said:
How did you deal with lash on the valves?
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I just did a leak down test with the cams off so all the valves would be closed. I got a ton of air coming out all of the exhaust valves and seems a little out the intake on each piston. Looks like I will need to take it back apart and make sure again all the valves are seated correctly. Also make sure I didn't miss anything when I cleaned the valves up.
 
I forget the technical name but the buckets that go over the valve stems are a wear item and need to be swapped out to hit spec
 
does the engine run? Any chance your compression tester is off?
 
Hol up, you did a leak test with the cams off? Don't the cams hold the valves down? Wouldn't it stand to reason that the valves are gonna lift if you blow air through them without anything to hold them in place and allow air through.

Would check valve lash and put in the cams
 
Was the block decked and honed? If there was damage prior, there can be warping on the head and block, plus cylinder damage.
 
just re read this. if air is escaping past the valves you need a valve job to make them seal correctly
 
Awafrican said:
Hol up, you did a leak test with the cams off? Don't the cams hold the valves down? Wouldn't it stand to reason that the valves are gonna lift if you blow air through them without anything to hold them in place and allow air through.

Would check valve lash and put in the cams
Click to expand...

pretty sure the valve springs would prevent that, without cams (and all springs still installed) all valves should be closed.
 
RyGuyv said:
pretty sure the valve springs would prevent that, without cams (and all springs still installed) all valves should be closed.
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Ah right forgot about the retainers on the springs. Derp, thanks for the catch, still seems odd to me to test without the cams installed ciWJgog.jpg
 
Awafrican said:
Ah right forgot about the retainers on the springs. Derp, thanks for the catch, still seems odd to me to test without the cams installed View attachment 28778
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Not standard forsure!

IF he is still leaking with the valves closed then i would agree with EB that the valves are not sealing properly.
 
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