pushrods what!?!

[Anonymous]

recently installed factory rebuilt 200 in my 67'' comet. Lets just say valve noise was greater than acceptable, so after I took it in to a "factory approved" mechanic he informed me I did'nt have nearly enough valve clearence (I think he said about 1/16th "), he proceeded to remedy the problem by installing push rods that were 1/4" longer than the originals. The motor sounds great now but my oil pressure gauge is running real high. lifters were oiling and the compression was good, so I'm wondering if the new rods might have been allittle overkill, wadda' ya' think. I'm still pretty new the whole htdraulic lifter thing, so thanks for whatever info you can muster.

 

[MustangSix]

Hydraulic lifters need to be set with a preload. In other words, there is zero lash between the rocker and valve and the pushrod should acutally be compressing the lifter from .050" to .100" when the valve is closed. The hydraulic design of the lifter maintains this zero lash to eliminate the need for periodic adjustments and to reduce noise.

It's possible that you may have gotten a reground camshaft that had a reduced base circle that reduced the preload on your lifters. Since the later small six had no provision for valve lash adjustment, the remedy was to install longer pushrods.