I Don't care what anyone says. Unless they have actually taken the time to do the measurements, I have no idea how anyone is getting less than a 7.400" pushrod with a .600"+ lift cam in an otherwise stock combo.

You need to MAKE SURE you are on the base circle of the cam before checking for proper pushrod length, then once you have the length with NO preload, add .050" to .075" to that measurement to determine the proper length.

Here is another method for use with or without a pushrod length checker:

FWIW, EVERY cam install I have done using the LS7 lifter with a cam with greater than .600" lift (read smaller base circle) AND stock heads w/GM MLS gaskets has taken 7.425" pushrods for ~.050"-.060" preload. We measure lifter preload on each and every cam install we do. I have never had a lifter failure nor do we end up with the dreaded "sewing machine" noise.

Its very simple, If you change ANY of the following:
valve sizes, valve job, head milling, thinner/thicker head gaskets, decked block, cam with an altered base circle, etc... YOU MUST CHECK FOR PROPER PUSHROD LENGTH.

I have helped countless numbers of individuals with this process over the phone, via email, and PM's. I've posted the process on at least 3 occasions.

Here it is again in a nutshell:

1. Using the EO/IC method, get the lifter to the base circle of the cam.
2. Using a known length pushrod (7.400" is a good start with stock rockers) run the rocker arm bolt down to zero lash. This is easily done with your fingers "wiggling" the rocker, the point at which the "slack" is just gone is zero lash.
3. Set your torque wrench to 22 lb./ft. Tighten the rocker to full torque and count the number of turns it takes to get there. 1 full turn wtih a stock 8mm X 1.25 bolt is ~.047" preload as measured at the pushrod/rocker interface.
4. I normally shoot for 1 1/4 to 1 3/4 turns with stock type lifters like Comp 850's, LS1, LS7 etc.

For an example, if you use a 7.400" pushrod and come up with 3/4 of a turn, you will need at least .025" longer pushrod to get into range. If you end up with 2 1/4 turns, you will need one .025" shorter...

I might not know everything but I will tell you that this method has worked for me year after year cam swap after cam swap. We average 3 cam swaps a week here so you can do the math.

If you are not familiar with the EO/IC method for determining valve events in a 4 stroke engine, its very simple:
For a given cylinder as the Exhaust valve is Opening, the intake lifter will be on the base circle of the cam and lash/preload should be checked for that intake valve.
For a given cylinder as the Intake valve is Closing, the exhaust lifter will be on the base circle of the cam and lash/preload should be checked for that exhaust valve.

THIS METHOD ALWAYS WORKS!!!

Check it using the above method and see where you are.


Also, here is a thread I posted regarding the whole LS7 pushrod cup issue:

https://ls1tech.com/forums/generatio...1-lifters.html

Please please please at least try the above method before you do damage to your valvetrain.

I can't tell you how many times a week I work with people who have taken bad advice from the internet and have destroyed their lifters, blown up rockers, brocken valvesprings, or in the best case, have a noisy valvetrain...

PLEASE STOP THE MADNESS!!!

/rant

Shane

 

Very good info and will check that way to make sure. When wiggling is that up and down or side to side movement?

Also for me seems very hard to tell of the valves are even moving I guess I need a pushrod and rocker snugged down to tell?

 

hey john lmk how that cam works out for u budd!.. im still having a hard time deciding who to go wit..

 

It's almost ready to go. Only hold up is the pushrods. I'll let you know how she feels

 

Any info on this?

 

Not sure I follow what effect the lift has on a measurement at zero lash unless you are saying that the larger lift could require changes to the rocker stand which would then alter the pushrod length.

 

Ok so following what you say I used a 7.4 and got it with a socket till felt almost no wiggle and got my tq wrench and counted turns till she clicked and it was 1 1/2 turns. What would that get me at? Thanks

 

Also just to make sure. When the exhaust pushrod starts to move up measure the intake and when the intake pushrods starts to move down measure exhaust?

 

Doing it that way its about a full turn

 

I come up with 0.091" of preload with 1-1/2 turns based on how mine measured using this method.

 

Sounds a lil high no?

 

Leaving the crank alone and using vettesnut method still get 7.375 I'm confused!!!

 

Vettenuts just make us a vid on setting up the right size pushrods so we can sticky it for future reference.U the man.Would anyone have a vid of setting em up right?I have looked on YouTube and haven't found nothing on the ls1.

 

Up top please. I'm getting 1 1/2-1 3/4 using shanes method and checking intake once exhaust goes up..what size PR is that?

And with vettesnut method I'm still getting 7.375 as my best rating with .75 preload

What is my preload and PR length with shanes method? And which one should I use?? Thanks I want this car running already LOL

 

1 1/2 - 1 3/4 turns with Shanes method equates to 0.071 to 0.082 of pre-load with whatever pushrod was in place.

 

I used a 7.4 pushrod. Hmm ill try it with a 7.375 and see

 

It's 1 1/4 with a 7.375

 

That (1 1/4 turn) is 0.059 of preload using Shane's formula.

 

So really then I could go any way either a 7.375 or a 7.400? But with preload best bet would be 7.400? Thanks

 

According to my calculations, that's 0.071". You can confirm during installation if you have a dial indicator.