charliemccraney (5/28/2009)
Ted, From your article, it sounds like the first thing I need to do is observe how the roller is traveling across the valve tip. That will tell me if I have to shim or trim the pedestals. When you are setting the geometry, how much do you change the height at one time? Charlie. I’m taking this opportunity to start a new post with your question.
Although I have a dial indicator setup that tells me exactly how much the geometry is off by measuring the rocker tip location both at zero and full lift, changing the rocker stand height in 0.025-0.030” increments will allow you to sneak up on the ideal position. When doing the initial setup, using washers of equal thicknesses or valve spring shims work well for raising the height. By working with only two of the stands while doing this also simplies the process. If you’re needing to lower the shaft, then having a pair of stands that are cut 0.150” shorter than stock and then raising these in set increments will allow you to determine what the final height of the stands needs to be.
charliemccraney (5/28/2009)
Now that I'm focused on the geometry, I took a closer look at the pattern on the stems. It is slightly off center - the pattern is shifted towards the exhaust side of the heads. Does this tell me anything regarding the geometry?
Due to manufacturing variances and/or any guide work that’s been performed since the heads were new, the rocker tip can be potentially sitting anywhere on top of the valve stem. But if the rocker tip is sitting outboard of the valve stem center at zero lift, then initial indications would be that the shaft is sitting too high. In an ideal world, the rocker tip should be sitting slightly inboard of the valve stem center (towards the intake) when the rocker is at zero lift and where ideal valve train geometry is present. In a less than perfect world, aim for the smallest contact patch on the valve tip between zero and full lift regardless of where the valve tip resides (within reason of course).Another tip is to run a straight edge across the valve stem tips with the rocker assembly removed to insure that all the valve stem tips are indeed at the same height. If you find that these are at varying heights, then it’s going to be difficult to accurately set up the valve train geometry.
Lorena, Texas (South of Waco)