5.3 advice
May 27, 2015 | 10:38 PM
#16
Thread Starter
Staging Lane
Joined: Nov 2014
Posts: 79
Likes: 15
From: omaha
Ok guys I must be ****** something up.. Im using a comp cam pushrod checker . useing my #1 and #3 cyl at tdc 7.250 at 0 lash (the point it has no up and down movement) Im i doing something wrong???? so with .075 preload i need 7.325 pushrod?
Last edited by madracer402; May 27, 2015 at 11:42 PM.
May 28, 2015 | 10:16 AM
#18
TECH Apprentice
Joined: Oct 2010
Posts: 363
Likes: 3
From: Houston, TX
ok hers mine. my milled .030" heads, ls7 lifters, and stock .051 mls head gasket. ls7 lifters want somewhere between .07-.09 preload.
im running 7.350" push rods. that takes 1.75-2 turns to get 22ft/lb, that puts me around .082-.094" of preload.
i used a push rod checker and tried 7.325" push rods and got 1-1.25 turns to 22 ft/lb. that is .047-.058" preload.
im running 7.350" push rods. that takes 1.75-2 turns to get 22ft/lb, that puts me around .082-.094" of preload.
i used a push rod checker and tried 7.325" push rods and got 1-1.25 turns to 22 ft/lb. that is .047-.058" preload.
May 28, 2015 | 11:11 AM
#19
The turns to preload method does not work. Don't use that method. Use a push rod length checker like you are. That is the only way to accurately get a preload measurement. 7.325" seems fine. Here is a post that explains how to use the checker in case you need it.
https://ls1tech.com/forums/generatio...l#post13174477
This is assuming you have the Comp Cams adjustable pushrod, which at its shortest length is 6.800".
Each turn of the adjustable 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 0.075" lifter preload, you add that to the measured number and you end up with 7.400" 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 adjustable 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 0.075" lifter preload, you add that to the measured number and you end up with 7.400" 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.
May 28, 2015 | 11:23 AM
#20
Teching In
Joined: May 2015
Posts: 23
Likes: 0
Also your cam base circle comes into play here. My factory cams base circle measured 1.560" while my new Comp Cam 212/218 cam measured 1.480". So if my math is right, the new setup will need .080" more push rod length right off the bat.