I just installed Magnm roller rockers, guide plates and pushrods in my 68- 455. Has anyone had experience with these (good or bad) also any tips for setting the preload would be helpful

 

Funny you haven't had any response on this. I've got a set of the Comp Cams stainless roller rocker arms bolted up... but I can't give you any feedback on them yet... the motor hasn't been run yet.

 

Its a decent set-up, they wont handle much valve lift or spring pressure. If they wont handle your cam profile then you need to move up to 3/8 screw in studs and full roller rockers anyway. In any case, pitch the pivot nuts that come in the kit and get a real set of polylocks with setscrews to lock the adjustments.

As far as valve lash, start with cylinder #1 at TDC (both lifters should be on the base circle of the cam). Slowly tighten the polylock until you get zero lash (lifter plungers has no preload, but no clearance). Turn the polylock 1/2 to 3/4 turn, then tighten the setscrew. Rotate the engine 90 degrees, lash the valves on cylinder #8. Rotate 90 degrees and #4, continue rotating 90 degrees and lash the valves in the same sequence as the firing order.

 

For me, I would never turn the polylock 1/2 to 3/4 turn. For me 1/4 turn at the most.
Gene

 

^^^^^^ I agree.

 

Thanks for the imput, I will start at a 1/4 turn and work from there. I didnt get the poly locks, if I run into trouble I'll change them out (I was concerned about the addtional height of the poly lock). I have an old steel valve cover, I am going to cut off the top so I can adjust the valves with the motor running like a small block chevy.