defining cam deviation

[Douglas Bath]

I'd like to understand what the the deviation is measured from: measured from the crankshaft or the exhaust cam. I just had the variocam pads changed but still have -9 degrees on one bank. Jake Raby says change your cam chain when you change your variocam pads. This was not done by my indie, but, can that short cam chain really result in several degrees of deviation? I would think the camshaft sensor is referencing the crankshaft sensor. This would mean the deviation would be the combined slop from the three chains. I'd like to have some confidence that going back in and installing a new cam chain (the short one) will really improve my situation.

[JFP in PA]

Welcome to RennTech 

 

Cam deviation is the difference from ideal between the crank position and the cams relative positions.  The specs for these engines are +/- 6 degrees.  Excessive "slop" in this system can come from multiple sources: The chains, the wear pads (particularly the small ones on the five chain engines), and the hydraulic tensioners, all of which are subject to wear/stretching.  Unfortunately, it is often very difficult to isolate the specific component causing the problem, resulting in the replacement of everything.

[Douglas Bath]

Right, so my indie chose not to replace the short cam chains when doing the pads, and apparently failed to replace the long chain guides (the ones that don't receive the tensioners). Bank 1 is now at -8.5. I'm pretty bummed out. 

[JFP in PA]

Common phenomenon.