No, the lifters don't cause that much difference, because once the engine is running, the lifters pump up to zero lash - but there is a geometry difference between a collapsed lifter and one that has no lash..... and that does cause a bad reading. What I was trying to do was see if I could use the collapsed lifters without shimming to zero lash to check the original cam C/L installation. One lifter needed shimming and the other did not. I was surprised to find the 5? difference in cam C/L installation.

So, I spent all day yesterday checking on the checking. First I swapped the 2 lifters and found the same cam C/L readings, so the problem wasn't with the lifters. Next, I considered that one follower could be bent. So, I swapped in all 6 followers on that cam and found them all within .5?. I didn't check the 6 from the other head because I assume the machinist disassembled one head at a time - and/or kept parts together. I'll call him today to find out. [EDIT - a call to him verified he did work on one head at a time - EDIT]

I haven't tried to move the water pump down since it's already final installed with a new gasket - but I don't think it could throw that one cam off by that much and in the advanced direction.

I think it has to be a misread on the original installation - not terribly surprising given the difficulty of setting these cam C/Ls with the hydraulic lash adjusters and the way I tried to install them using a fabricated solid lifter and the OE spring rather than checking springs. When I examined the fabricated "solid" lifter that I originally used, I found that it had slightly collapsed from the pressure of the OE spring.... that's likely where the error was made.

I'm surprised that with a 5? cam C/L difference the extra power on one side didn't make the truck run in circles or flip over. <img src="/forums/images/graemlins/lol.gif" alt="" />

I now have one cam where I want it, but couldn't find a combination of sprocket tooth engagement and cam bushing that would set the passenger side where I want it, so I've ordered another set of bushings from Summit. I'll make one more attempt to set these up like I want them before I go back to the original truck cams.

I don't know which I like least - cam bushings or followers with hydraulic lifters. <img src="/forums/images/graemlins/baby.gif" alt="" />

Frank