help with getting pushrod size (VIDS)
#21
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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
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
#33
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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.
#34
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
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
#35
TECH Addict
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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
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
Last edited by Darkman; 06-26-2011 at 04:23 PM.