dirt track racer 81

iTrader: (45)

Im sure there's a 100 threads on this. The deal is my truck started running bad a few weeks ago and pulled the cam out just to make sure a lobe wasn't screwed up or anything. Got to looking at the push rods and one was screwed up and was almost a 1/4 inch shorter and other were worn differently, you can tell they were not spinning.
It's got L92 heads milled .030 with what I thought were Comp OE lifters, .040 Cometics and PRW 7.35 push rods.
I got a push rod length checker, with the lifter on the back side of the cam I can only get .018 preload before the valve starts to open. Is the valve supposed to open?
Just from doing a little searching people are putting .060-.080 preload on the Comp OE lifters and .002.004 on the Comp R lifters.

02Reaper

iTrader: (2)

The valve is not supposed to open. From what I can recall, you are supposed to get the lifter just long enough so you can roll it between your fingers easily, without it being able to move up and down. Then you just add the amount of preload you want to whatever you have on the rod.

budhayes3

iTrader: (19)

x2, get the pr checker so that it's fully extended and touching the lifter and rocker without opening the valve.

dirt track racer 81

iTrader: (45)

Once I get 0 lash and go to tighten the bolt down to preload the lifter I can only get .018 preload. I make the checker any bit longer to get more preload the valve will open. Doesn't this need .060+ preload? Am I doing this wrong? First time to really check push rod length. Im used to solid flat tappet lifters not hydraulic lifters.

bullygoat

You're measuring wrong. You need to have the rocker seated fully and the lifter on the bottom of the lobe. Then you lengthen the adjustable pushrod until it takes all of the slack out. Then you add what preload you want to the length of the pushrod. So if the pushrod length checker extends to 7.300" and you want .050" preload, you'd order a 7.350" pushrod.

Robert91RS

iTrader: (2)

^I assumed thats what he was doing....

Is the lifter stuck maybe?

budhayes3

iTrader: (19)

Have you tried on a few different valves too see if the above statement applies?

dirt track racer 81

iTrader: (45)

I stuck some pushrods I had on a few other valves and they opened. I'm kinda wondering if by chance I got the comp R lifters and not the oe lifters.. I'm going to do what bully said just get to 0 lash and then make the checker .050 longer and see how that does when I tighten the rocker down.

bullygoat

If the lifters are pumped up, they are going to push the valve open no matter what you do. That's why you just adjust to zero lash and add your preload to that measurement. But you need to know what lifters you have so you do add the correct preload.

JDC

iTrader: (3)

You need to tighten the rocker down first and then adjust the pushrod to zero lash and measure it and add what you want for preload.