![]() If I can get through, I'll also try to get the official word on the valve timing. I'll be calling MoCo tomorrow to get some insight on that. I also ran into something really odd that I can't talk about that may make my motors different from everyone else. I wouldn't put much money on that, since my measurements were so bad. It seems that the intake ?may? be the same front and rear, but the exhaust opens and closes later on the rear. Though my measurements were not very accurate, I do believe there is more valve overlap on the rear cylinder than the front. It's really difficult to get a probe on the valve bucket with that darn compression release gizmo in the way. I spent an hour out there and came to the conclusion my measurements were not very accurate. I pulled the covers off my spare motor, attached a degree wheel, and tried to make the appropriate measurements. Ok, now I know that verifying valve timing can be a real challenge. I'm on my way out to see what the degree wheel says. If the cam sprockets do what I think they do, there is a curious difference between "Cam timing" and "Valve Timing". The "Cam Timing" numbers from the service manual are not clear to me since they don't say what they are measured relative to (i.e. ![]() ![]() "The automatic compression release (ACR) has its greatest effect on the front cylinder because of differences in valve timing between front and rear cylinder." Per my 2003 service manual table 3-37 (Cylinder Compression):Īlso, just below that table are these words: I understand they are the same cams front and rear, but I'm still suspicious about the way the sprockets are bolted on the end of the cams. Since each cylinder is completely independent of the other at the slow RPM that compression tests are done (exhaust dynamics not in play), how could the compression be WILDLY (100psi) different if the internal head/cylinder volumes are identical, valve timings are identical, and compression release is identical? The only way I could explain the huge differences in compression (psi) would be if there was some difference in valve timing. Click to expand.Rick, I don't see how the angle between cylinders has anything to do with the compression measurement (psi) or the compression release.
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