bones5133

iTrader: (1)

So I have read a couple different articles on doing push rod length and I came up with the one from comp cam site that says:

Adjustable push rod base length + Number of turns X .050 = New Length

In my case this would be:

6.8 + (10 X .050) = 7.3

I have seen another article on here that shows :

Take the # of turns and multiply that number by 0.050” Add 6.80”. (This is the length of the checker) Now add lifter preload* This is your pushrod length

Looks like this: 10 (turns) x 0.05” = 0.5” + 6.8” = 7.3” +0.075”= 7.375”

I am building a 6.0L I had the heads milled .030" and I am running LS7 lifters.
1.Does this sound correct for my pushrod length?
2.What is the difference between the formula why did one add lifter preload?

Also How I check the length was I brought the engine to TDC then I put the adjustable push rod in there with 9 turns and tapped on the rocker and there was play up and down. Then moved it to 10 turns tightened it down and there was no play up and down. Is this method ok?

Thanks
Trever

ckpitt55

iTrader: (4)

The first method (without adding preload) gives you your "zero lash" value. That alone is useless to you.

You need to add your desired lifter preload to your zero lash value, otherwise you won't get any lifter preload. You need lifter preload unless you enjoy breaking stuff. Say your zero lash length ends up being 10 turns from fully closed and you ultimately want .080" lifter preload. That means you'd order 7.380" pushrods (6.8 + 10*(0.050) + .080)

As far as finding your zero lash length - all you have to do is make sure that you're on the base circle of the cam. Rotate the engine over and watch the checker tool rise and fall. After it stops moving you can install your rocker arm and make your zero lash measurements. How zero lash should "feel" is kind of subjective - I went for as little play as I could muster without being tight to the point of binding.

bones5133

iTrader: (1)

Ok that makes sense. So If my base is 7.3 Is it a preference thing on how much preload I would like? Does the LS7 have a recommended pre-load?

Do these values seem right for what I have done with my heads?

bones5133

iTrader: (1)

I have read .080 is a safe number for preload. agree or disagree

baronsmith98

iTrader: (2)

I just went through this myself .080" seems to be a good preload for ls7 lifters. When I was checking my pushrod length I put an indicator on my valve and backed out my pushrod checker until it just moved my indicator (loaded the valve maybe .001 or .002") to make sure I was at zero lash. I also torqued my rockers during this process as we'll to make sure it was accurate. I then took a rough estimate of the amount of turns, I know I had already went 8 and I was in the ballpark of a little over half a turn probably around 8.6 turns.

I will let you know I checked mine without head gaskets because I did not have them yet and just added the gasket thickness to my overall length.

So 6.8 + 8.6 x .05 = 7.23

Then take 7.23 + .045 ( head gasket thickness) + .080" ( desired preload) = 7.355
This measurement is only .005 off of 7.350" length pushrods so I went with them.