school me on lifter pre-load and valve lash...

[Boss 351]

I've been having trouble with my rockers the setup is as follows: Heads machined for 7/16 studs, 1.6 roller rockers, hardened pushrods, comp cams, guide plates, stock hydraulic lifters.

I know the "plain" way of doing this is tightening the rockers until the pushrods start to tighten (by turning them with your fingers) and then turn the rocker nut by 1/4 or 1/2 turn and lock into place and ZERO valve lash.

My problem is that I'll either end up with a loose valvetrain which ticks like a diesel (and not run properly since the valve timing is off) or one or two valves stay open causing my engine to run on 6 or 7 cylinders. Good thing I can remove my valve covers WITHOUT having to remove the upper intake.

I went and got a dial gauge and magnetic base so I can adjust the lifter preload properly, I'm not sure what the preload should be; is it .020??? Or should I put the dial on the valve to watch and make sure the valve doesn't move while I attempt at turning the rocker nut 1/4 or 1/2 turn? The lifters will be charged since the engine would have run a couple of minutes prior to removing the valve covers.

 

[GT_Rich]

Man, I was in your exact situation over the winter (it was my first time doing stud mount rockers). The first time I had two valves hanging open, the second time I had ticking. Here's the best advice I have:

If you have an extra valve cover (an old stock one would be perfect) cut off the top and inside edge, and use the outside three bolts to bolt it down. Doing one side at a time, adjust the rockers with the motor running. All you have to do is loosen the nut until you start to hear a tick, and then tighten it down just enough to stop the tick - then lock it. Once one bank is done, switch the cut up valve cover to the other side and do it again.

This not only worked great but gave me a better understanding of how much preload the lifters really give with the motor running. Don't be intimidated by this concept - it's easy!

 

[Boss 351]

that's an idea (old school)... but if you put too much preload, at WOT the lifters won't have enough time to bleed the oil and basically becomes a solid lifter and will cause the valves to float. I'm going to try and find the correct preload and attempt that and if THAT doesn't work I'll try the old school way of adjusting the rockers with the engine running

 

[GT_Rich]

Ha - you'd be surprised. I had mine set at zero lash plus 1/2 turn (engine off) and when I went and adjusted them with the engine running, I had to take 1/4 to 3/8 of a turn OUT of each one. Hydraulic lifters do not need very much preload to run without sounding like a chatter box. Give it a try and you'll see