302 stepchild needing some valvetrain guidance

[timdhawk]

Hello Gents...
I say stepchild because I have a 74 302 in in a 1950 mercury!
I have the torque down positive stop type rocker studs (pressed in, not threaded). After an engine rebuild (essentially stock still but with a very mild new Comp cam) I swapped over to roller tip style rockers with new hydraulic lifters and new pushrods. After doing the engine break in we noticed the valve train was noisier than we liked. (I know roller tips can be more noisy in general). We pulled the covers and quite a few random rockers were excessively loose even with the nuts still torqued correctly. Some pushrods had approx. 1/16" or so of lash. Even when we swapped back in some of the old parts to check things, they still had some free play. The stock length rods are 6.881 and a friend had some 6.936 rods so we gave them a shot. It ran ok, but it ran better on the shorter ones. I can't seem to find any pushrods that are in between those 2 lengths so my question is this...
Is there anyway to shim these type of rockers to take up the lash, and/or give the approp. amount of preload on the lifters?

Thank you!

 

[LILCBRA]

I guess I never realized there was an actual torque spec to the stock rocker arms, but I guess it would make sense on an assembly line. Since I've never rebuilt a stock engine, where does the nut stop to read torque? Is it at the end of the threads or are the rockers supposed to bottom out? I don't remember the rockers bottoming out, but it's been a lot of years since I've seen a stock valve train setup. So that would lead me to believe the nuts are bottoming out on the threads.

In that case, it sounds like you'll need some round shims or maybe a washer or two. You'll also most likely need a new locking nut to use with the rockers since you'll most likely not be using a torque spec. Then you'd have to go about adjusting the rockers as most any other aftermarket rocker is adjusted: assure the valve you're working on is fully closed. Tighten the rocker nut while spinning the push rod until you feel minimal up/down movement and there is a slight drag. Don't over-tighten as you will start to compress the hydraulic lifter. Move on to the next valve and repeat. If you need further guidance there are YouTube videos on how to do this. You'll ignore torque specs using this method and you'll need to ensure that your rocker nut isn't able to back out which is why I suggested new locking nuts.

This is all assuming your valve train geometry is right. In your case I'd imagine the stock push rods you pulled from the engine are correct. Hopefully this helped point you in the right direction. Good luck!

 

[Enzio]

I did not think that pressed in studs went with positive stop rockers. But if so, then check to see if the studs are pulling out.