Roller Rocker Adjustment Question

De-Marko

New Member
Oct 6, 2014
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Hey!

I wanted to pick your guys brain to see what you guys think about this question in regards to the rockers.

First, I have a 327 stroker in an '89 mustang GT with GT-40X heads and the Ford X-cam. I also have the FMS pedestal mount rockers. My problem is, is when setting with shims I'll tighten the bolt up till I get to zero lash, I torque the rocker bolts to 20 ft. lbs. which takes about half a turn. While tightening the rocker slightly pushes in on the valve. I am at the base circle of the cam. Do I need to shim further? I'm up to .090 already with the FMS shim kit otherwise the rocker opens the valve. I am using the stock length push rods. What do you think?? Thanks!
 
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If you haven't you need check for correct push rod length. My card needed a custom push rod length and I still really don't know why it did but the previous owner of my car vault a long block from Seagrove engines in North Carolina we pulled the cam out of it and put a Trick Flow stage 1 in it we put it all back together and it had awful valve train noise pulled it back apart check for correct push rod length and ended up needing a custom push rod no joke. really shouldn't be all that much adjusting on a pedestal mount rocker correct?
 
No Mike, I didn't measure for the pushrods and I agree the shimming is up there! Based on that it seems I'd have to go shorter on the rods; sound right? I have access to an adjustable pushrod that I'll throw in there and see what's up.

Super, That's crazy, did you go longer or shorter?
 
You might be cranking it down too much at 20 ft lbs. You may be pushing the lifter plunger too far down then trying to make up with shims. I had this same problem. Do you have the intake off? Are these new lifters? The problem is, with new lifters that have not yet been filled with oil under the pressure of a running engine, the 20 ft lb tq is pushing the lifter preload way past where it should be. This would have the same effect of a pushrod being too long.

I'd ditch the 20 ft lb method and measure lifter preload and shim to get that within range. Then, see how many shims that takes. Trust me, I when through this myself. There's a thread on here somewhere. I'll see if I can find it.

In the end, I dont disagree with the possibility that valve train geometry may need to be looked at and concluded by a professional. However, it could just be a matter of understanding lifter preload and ditching the lame instructions that come with the rockers.
 
If I can remember, mine are shimmed .060 with 3/4 turn down from zero lash. I've had no problems and put lots of miles on it. However, if your engine has been rebuilt with various machine work being done, as the others have said, shorter pushrods might be where you need to start. Remember though, even with shorter pushrods, there can be differences in the valve machining from valve to valve. So, you will still want to check actual lifter preload on each valve and shim accordingly.
 
Thanks John, right on! The lifters I bought new but have have several thousand miles on them, and unfortunately the intake is not off. I'm just going to have to really get in there and check everything...I'm sure the pushrods may be whats up. Thanks for the response!