How to check for proper pushrod length???
05-03-2011, 01:20 PM
#1
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How to check for proper pushrod length??? Ok so i will be getting new rocker arms and i hear so many different ways to check the proper pushrod length??? Some people say you cant with hydraulic lifters unless they are pumped up (car running) another person said it will only be slightly off with the car not running.. i have an adjustable pushrod from jegs. the heads are on the car with LS^ springs on it and im ready to do this. Do i need the piston TDC im assuming so there is no load on the arm. do i need light springs to test? if the motor isnt running and the arms are tight should there be any play in the rocker arm itself? i think my heads are milled around .025 pushrod and cam in sig. Stock ls1 lifters with 3 k miles on them. Got the cam used for a very good deal. Not sure the base lobe or the maker...
05-03-2011, 01:48 PM
#2
Best way is to turn the motor over by hand till exhaust valve is fully open and check the intake side...then turn the motor over by hand till the intake valve is all the way open and check the exhaust side.
Turn your adjustable pushrod in until you can just freely spin it with your rocker torqued then measure it.
If you want .070 preload and you get s measurement of 7.330" on your adjustable pushrod you add .070" to it to get a 7.400" desired pushrod
Turn your adjustable pushrod in until you can just freely spin it with your rocker torqued then measure it.
If you want .070 preload and you get s measurement of 7.330" on your adjustable pushrod you add .070" to it to get a 7.400" desired pushrod
05-03-2011, 04:19 PM
#3
Here is my method:
Each turn of the pushrod is 0.050". When fully closed, it is 6.800". This is pushrod "gauge length" so you can't measure it directly as the pushrod length is actually based on the length between the ball ends where the ball end measures 0.140" in diameter. Assuming you are using stock rockers or a non-adjustable rocker.
1. Open the adjustable pushrod to the same length as your stock pushrods
2. Close it down two turns
3. Put your rocker rail on the head
4. Make sure you cylinder (typically #1) is at top dead center on the firing stroke so both valves would be closed
5. Put the pushrod in place on the intake valve and make sure it is in the lifter cup
6. Install the rocker and snug down the bolt (don't need to torque, just make sure it is snug)
7. Lift rocker tip up and down, if it "ticks" the pushrod is too short. If you can't easily move the rocker the pushrod is too long.
8. You can try and adjust the pushrod in place but my fingers are too fat so I end up pulling the rocker and adjusting the pushrod length. Go either shorter or longer 1/2 turn and try again.
9. You are trying to get to the point where the lifter doesn't "tick tick" with the pushrod in place nor is the rocker snug. When you get the pushrod length such that you just barely get rid of the "tick tick", you have found "zero lash".
10. When you have found zero lash, carefully remove the rocker and pushrod without rotating the pushrod.
11. Tighten the pushrod until it is fully closed counting the turns as you go.
To figure out your pushrod length you do the following. Let’s assume it took 10-1/2 turns to close the pushrod down to its shortest length after you reached zero lash. Each turn is 0.050".
Your length is then: 6.800" (fully closed length) + 10.5 X 0.050" (number of turns times the length change per turn) = pushrod length minus preload. So for this case:
6.800 +10.5 X 0.050 = 7.325"
This is the length you measured to zero lash without any lifter preload. Now let’s say you want to have 0.100" lifter preload, you add that to the measured number and you end up with 7.425" pushrods.
Now repeat for the exhaust valve to verify the length. If you have something like Yella Terra's, it is the same procedure but you must snug down the rocker pair rather than the single rocker.
Each turn of the pushrod is 0.050". When fully closed, it is 6.800". This is pushrod "gauge length" so you can't measure it directly as the pushrod length is actually based on the length between the ball ends where the ball end measures 0.140" in diameter. Assuming you are using stock rockers or a non-adjustable rocker.
1. Open the adjustable pushrod to the same length as your stock pushrods
2. Close it down two turns
3. Put your rocker rail on the head
4. Make sure you cylinder (typically #1) is at top dead center on the firing stroke so both valves would be closed
5. Put the pushrod in place on the intake valve and make sure it is in the lifter cup
6. Install the rocker and snug down the bolt (don't need to torque, just make sure it is snug)
7. Lift rocker tip up and down, if it "ticks" the pushrod is too short. If you can't easily move the rocker the pushrod is too long.
8. You can try and adjust the pushrod in place but my fingers are too fat so I end up pulling the rocker and adjusting the pushrod length. Go either shorter or longer 1/2 turn and try again.
9. You are trying to get to the point where the lifter doesn't "tick tick" with the pushrod in place nor is the rocker snug. When you get the pushrod length such that you just barely get rid of the "tick tick", you have found "zero lash".
10. When you have found zero lash, carefully remove the rocker and pushrod without rotating the pushrod.
11. Tighten the pushrod until it is fully closed counting the turns as you go.
To figure out your pushrod length you do the following. Let’s assume it took 10-1/2 turns to close the pushrod down to its shortest length after you reached zero lash. Each turn is 0.050".
Your length is then: 6.800" (fully closed length) + 10.5 X 0.050" (number of turns times the length change per turn) = pushrod length minus preload. So for this case:
6.800 +10.5 X 0.050 = 7.325"
This is the length you measured to zero lash without any lifter preload. Now let’s say you want to have 0.100" lifter preload, you add that to the measured number and you end up with 7.425" pushrods.
Now repeat for the exhaust valve to verify the length. If you have something like Yella Terra's, it is the same procedure but you must snug down the rocker pair rather than the single rocker.
05-03-2011, 07:17 PM
#5
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vettenuts' method is almost exactly what I used(my hands are also big so i had to take the pushrod length checker out and adjust each time), and it is effective, simple and cheap to do; but going with the assumption that you are using hydraulic lifters, as you do this point
try to get a feel for what 'just barely snug' is right before you start to compress the lifter because you can easily overtighten (thus mildly compressing the lifter) and think its perfect, which will throw off your measurements. And triple or quadruple checking is well worth it, considering the hassle and possible damage of not getting it right...
Also, i used a piece of tape to keep the pushrod length checker exact as i don't know about yours but mine was a bit loose and would not be where i set it when i remove it.
Also, i used a piece of tape to keep the pushrod length checker exact as i don't know about yours but mine was a bit loose and would not be where i set it when i remove it.
