making my own cam tower shims

[Jeff G 78]

I went the other route and didn't shim or change the valves. I modified the cam gear to get the timing right and the chain guides to get the tension right. Works great on my race motor that sees continues high rpm use for hours at a time.

[Diseazd]

Jeff.....Where did you get your numbers to do the P79 conversion you did. Was this something that was proven engineering or did you do this on your own using trial and error. Why don't you do a thread with your numbers....I know you have photos. How much did you shave off and why? Etc. Etc.

[rossiz]

@JeffG - can you point us to a thread on how you modified the cam? i'm looking to do something similar (shave a p90 on an f54 with cam, but for the street) and i've been thinking about turning back the cam vs. all the shimming. i've seen eccentric cam bolt inserts - is this what you did?

[Jeff G 78]

Yes, I did the eccentric shims in the cam drive. I followed the "How to Modify..." book. The shims came from Summit Racing and they are for a SBC. You need the cam setup sheet, a degree wheel, and a good dial indicator with stand, but the just isn't terribly hard once you are setup. I will post pics of what I did tonight or tomorrow when I have more time. I'm sure I have posted what I did somewhere here. It might be in Guy's engine thread.

[240260280z]

The chain guides and chain tensioner are adjustable. If you shave the head and take the front timing cover off, you can easily take up all of the slack from the shaving. An adjustable cam will let you dial in the mechanical valve to crank timing.

In my case I shaved 2mm off an N47 and did not bother taking off the timing cover. I correctly assumed the tensioner would take up the slack. I had to rotate the cam 1 link CW closer to get the mechanical timing close enough to use the hash mark/triangle alignment marks. It was a quick and dirty ghetto mod thought experiment that I implemented.

FYI it is a common improvement mod to use a larger chain guide bolt(s). Check the How To Modify.... book for the details

Edited May 29, 2014 by Blue