I have a Hummer H3 that I put a cylinder head on. I have a code for exhaust cam to crankshaft correlation. I pulled the valve cover off and checked the flats on the back of the cams. The intake cam was level and the exhaust was off. I advanced the cam one tooth and reassembled it. I started it up and I have the same code. I pulled it back apart and rechecked the cams. The exhaust cam was off in the opposite direction. I retarded the cam one tooth. The exhaust cam is still out of time. I can't put the chain on with the cams in time. Is it possible for the cam phaser to be bad and how do I check it? Before I pulled the head the cam timing was spot on.

 

it could be a stretched chain.

 

What he said....
and the tensioners worn out.

 

I had checked the cam timing before disassembly and the cams were in time with each other. I marked the sprockets and chain before disassembly and put it back the way it came off. Now the cam timing is half a tooth off. If it was a stretched chain I would think that i would get correlation errors on both cams because of the length distance between cams and crank. It's just the exhaust cam.

 

did they shave the head and did you compensate for the amount shaved in the head gasket thickness

 

I'm not sure what was done to the head. I ordered the head, it was shipped to me and I installed it. I then sent my core back. I have no specs on machine work done on the head. I will have to call the machine shop. I called the machine shop, they said they shaved 0.005 off the head. That shouldn't be enough to cause my problem. If it did affect the timing it would be on both cams not just the exhaust. I have a new theory: If the bore in the cylinder head for the cam actuator solenoid was damaged or out of round, could oil pressure bypass the solenoid and cause the cam phaser to retard timing on camshaft? I swapped out the soleoid with another from a running vehicle and still have the code coming up.