I have a 455 my father built many years ago and was never run. I recently installed in my vista fired up and broke in cam. Valve train was a little noisy so i pulled valve covers. Thinking flat cam lobe all look fine but all of them have very little preload. It appears to have the comp cams roller rockers in it .Pushrod are 9.65 The problem is i cant get but 10 thousands preload before jam nut bottoms out on treads .This has 7/16 thread in head and 3/8 stud .I checked pushrod length and rocker is running right in center of valve. Cant seem to find shorter studs that size. This is on G heads. Any suggestion are appreciated.

 

Comp Cams magnum 5/16" pushrods #7659-16 are 9.70" long; #7660-16 are 9.75" long.

 

Just a suggestion . . .

Have you thought about a set of adjustable length pushrods?

 

Yeah, I’m gonna get me an adjustable push rod. See if 50-60 thousandths doesn’t mess with rocker to valve it’s real good now.Thanks.

 

Depending on the lifter will determine the actual amount of preload. Since you don't know much about it, anywhere between .030 to .060 into the lifter should work. 1/2 a turn to 3/4 after zero lash should work. This would be at operating temp.

 

stick a washer or shim under the jam nut. that’ll give you more jam nut adjustment . you don’t need adjustable p rods

 

That's what I was thinking. Thanks

 

I know I'm a bit late to this party, but....

Here is how I set lifter preload, and I doubt anyone will do this. The most important thing you need to know if how much travel there is in your lifter. I takethe lifter apart and actually measure the max travel of the lifter. Then I will typically try to set preload to be about half of this distance. You can calculate that by knowing your thread pitch and then back calculate how many turns to get that preload. If you don't know the travel of the lifter, and they all vary a LOT by manufacturer, you really can't say give it x amount of a turn.

jerry