bluz28

What's the optimum pre-load/ pre-load range to use?

Thanks!

Marc 85Z28

I set mine at .080" back in 2007 when I built my engine. Spins clean to the 7200rpm limiter with no abnormal/sewing machine noise. Nobody knew what was optimal then, and now it varies depending upon who you ask. I've heard as little as .050" and as much as .120"

bluz28

So do you think .0411" preload would be fine(quiet), my wipe pattern looks centered and about 1.5mm wide(1/16") with the 1mm shims supplied with my YT 6645 rockers, btw preload is 7/8 turn with factory bolts torqued to 22ft.lbs.?

Marc 85Z28

~.040" is not enough - it will be noisy. IMO you want at least .060" GM sets them to between .080" and .100"

Why are you using Yella Terras? Unless you're running an altered valve angle and set up the entire valvetrain PERFECTLY, they're going to cause valve control problems.

bluz28

Thanks, I was starting to get the feeling that my pre-load was on the low end so I just ordered some 7.450" pushrods, that should put me up to .066" pre-load. I've so far heard anywhere from .03-.08", .05-.08", and that .04" would be good, and a couple .08-.100", so it's been very frustrating trying to get a good understanding on the best preload range
BTW, I just installed AFR 205 w/66cc chambers w/PAC 1521 springs, and gm mls head gaskets. The cam also has LSL lobes (227/231 111 lsa+2).

The YT's I bought several yrs ago, and had never got around to installing them before. I guess if I have any issues with them I'll remove them(hopefully not).