Questions About Lifter Preload and Pushrod Length
10-27-2011, 09:10 PM
#1
Questions About Lifter Preload and Pushrod Length Ok well i have a couple questions im hoping some people who know the answers and maybe some sponsors can chime in.
Q1- How much lifter preload is ideal for LS7 lifters? 0.050, 0.060?
Q2- Using the EO/IC method to get the lifters on the base circle of the cam i came up with 7.350 Intake pushrod length and 7.3625 exhaust length. how i did this was by extending the comp cams pushrod length checker to 11 turns for the intake and 11.25 turns for the exhaust. than i multiplied each of those numbers by 0.050 and than added those totals to 6.800. thats how i came up with 7.350 Intake and 7.3625 exhaust. than i slid the pushrod length checker into the head and down into the lifter and tightened the rocker to 0 lash. i than tightened the stock rocker bolt to 22ft LBS and counted the amount of turns to get there. both were 1.5 turns. Am I doing this correct?
Q3- Am i supposed to add the lifter preload to the length i get from the pushrod length checker?
example: 7.350+0.050= 7.400 pushrod?
Q1- How much lifter preload is ideal for LS7 lifters? 0.050, 0.060?
Q2- Using the EO/IC method to get the lifters on the base circle of the cam i came up with 7.350 Intake pushrod length and 7.3625 exhaust length. how i did this was by extending the comp cams pushrod length checker to 11 turns for the intake and 11.25 turns for the exhaust. than i multiplied each of those numbers by 0.050 and than added those totals to 6.800. thats how i came up with 7.350 Intake and 7.3625 exhaust. than i slid the pushrod length checker into the head and down into the lifter and tightened the rocker to 0 lash. i than tightened the stock rocker bolt to 22ft LBS and counted the amount of turns to get there. both were 1.5 turns. Am I doing this correct?
Q3- Am i supposed to add the lifter preload to the length i get from the pushrod length checker?
example: 7.350+0.050= 7.400 pushrod?
10-27-2011, 09:18 PM
#2
Q4- If 1 full turn of a stock rocker bolt is 0.047 preload after 0 lash than my 1.5 turns to get the bolt to 22ft LBS would give me 0.0705 preload. Is this too much?
I put my stock pushrods in there and using the EO/IC method same as above it was a little more than 2 turns. So obviously i need a smaller pushrod than my stock LS1 rods. Im just really confused because i was told to use 7.425 pushrods but if my stock ones are too long than the 7.425 pushrods are way too long.
I put my stock pushrods in there and using the EO/IC method same as above it was a little more than 2 turns. So obviously i need a smaller pushrod than my stock LS1 rods. Im just really confused because i was told to use 7.425 pushrods but if my stock ones are too long than the 7.425 pushrods are way too long.
Last edited by 99 Blue Bird; 10-27-2011 at 09:27 PM.
10-28-2011, 01:13 AM
#4
Q2- Using the EO/IC method to get the lifters on the base circle of the cam i came up with 7.350 Intake pushrod length and 7.3625 exhaust length. how i did this was by extending the comp cams pushrod length checker to 11 turns for the intake and 11.25 turns for the exhaust. than i multiplied each of those numbers by 0.050 and than added those totals to 6.800. thats how i came up with 7.350 Intake and 7.3625 exhaust. than i slid the pushrod length checker into the head and down into the lifter and tightened the rocker to 0 lash. i than tightened the stock rocker bolt to 22ft LBS and counted the amount of turns to get there. both were 1.5 turns. Am I doing this correct?
How you are supposed to use the adjustable pushrod is to find how many turns for a pushrod length that will give you zero lash ... then add the amount of pre-load you want to that length. From how you describe it above, they were already at a length to give you ~0.071 pre-load (ie, 1.5 turns to 22 ft-lbs on rocker arm bolt). I don't really understand how you came up with the number of turns you did.
10 turns x 0.050 = 0.500"
6.800 + 0.500 = 7.300" (pushrod length for zero lash)
Now add pre-load of 0.082" --> 7.300 + 0.082 = 7.382"
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Gen2-LT4 (10-21-2022)
10-28-2011, 05:42 PM
#5
See attached chart. The LS7 lifters are supposed to have 2.09 mm = 0.082" pre-load.
So what led you to turn the adjustable pushrod to 11 and 11.25 turns?
I opened the adjustable pushrod length checker to 11 and 11.25 turns because i first put in my stock LS1 pushrods which are 7.400 length as described in the link i posted above and found that when i used the EO/IC method of getting my lifter on the base circle of the cam and torqued down the stock rocker bolt to 22 ft Lbs it took a little more than 2 turns to get to 22 ft Lbs. And by shanes method as posted above you want to be between 1.25 turns to 1.75 turns. So since the 7.4 pushrod was too long(and would be 12 turns on the pushrod length checker) i turned the pushrod length checker to 11 turns to get to 1.5 turns on the rocker bolt. Also, why is there a different length for intake vs. exhaust on this setup?
There is a different length between the two because in order to get the exhaust rocker bolt to 1.5 turns like the intake rocker bolt to both have 0.0705 preload i had to extend the checker a .25 turn.
How you are supposed to use the adjustable pushrod is to find how many turns for a pushrod length that will give you zero lash ... then add the amount of pre-load you want to that length.
I tried that way first but i could not get the top half of the checker to extend. Instead of just the top half of the checker spinning the whole checker was spinning in the lifter cup. So i decided to uses shanes method with a pushrod length checker.
From how you describe it above, they were already at a length to give you ~0.071 pre-load (ie, 1.5 turns to 22 ft-lbs on rocker arm bolt). I don't really understand how you came up with the number of turns you did.
Because a stock pushrod which is 7.400 length would equal to 12 turns on my pushrod length checker. So since they were too long i shortened the checker by a half turn each time. Which is how i got to 11 turns for the intake and 11.25 turns for the exhaust.
Only if you first find the pushrod length required to just give you zero lash with NO pre-load on the lifter. Then add how much pre-load you want. For example, if the adjustable pushrod needed 10 turns to give you zero lash, and you wanted 0.082" pre-load for a LS7 lifter, then it would be:
10 turns x 0.050 = 0.500"
6.800 + 0.500 = 7.300" (pushrod length for zero lash)
Now add pre-load of 0.082" --> 7.300 + 0.082 = 7.382"
So what led you to turn the adjustable pushrod to 11 and 11.25 turns?
I opened the adjustable pushrod length checker to 11 and 11.25 turns because i first put in my stock LS1 pushrods which are 7.400 length as described in the link i posted above and found that when i used the EO/IC method of getting my lifter on the base circle of the cam and torqued down the stock rocker bolt to 22 ft Lbs it took a little more than 2 turns to get to 22 ft Lbs. And by shanes method as posted above you want to be between 1.25 turns to 1.75 turns. So since the 7.4 pushrod was too long(and would be 12 turns on the pushrod length checker) i turned the pushrod length checker to 11 turns to get to 1.5 turns on the rocker bolt. Also, why is there a different length for intake vs. exhaust on this setup?
There is a different length between the two because in order to get the exhaust rocker bolt to 1.5 turns like the intake rocker bolt to both have 0.0705 preload i had to extend the checker a .25 turn.
How you are supposed to use the adjustable pushrod is to find how many turns for a pushrod length that will give you zero lash ... then add the amount of pre-load you want to that length.
I tried that way first but i could not get the top half of the checker to extend. Instead of just the top half of the checker spinning the whole checker was spinning in the lifter cup. So i decided to uses shanes method with a pushrod length checker.
From how you describe it above, they were already at a length to give you ~0.071 pre-load (ie, 1.5 turns to 22 ft-lbs on rocker arm bolt). I don't really understand how you came up with the number of turns you did.
Because a stock pushrod which is 7.400 length would equal to 12 turns on my pushrod length checker. So since they were too long i shortened the checker by a half turn each time. Which is how i got to 11 turns for the intake and 11.25 turns for the exhaust.
Only if you first find the pushrod length required to just give you zero lash with NO pre-load on the lifter. Then add how much pre-load you want. For example, if the adjustable pushrod needed 10 turns to give you zero lash, and you wanted 0.082" pre-load for a LS7 lifter, then it would be:
10 turns x 0.050 = 0.500"
6.800 + 0.500 = 7.300" (pushrod length for zero lash)
Now add pre-load of 0.082" --> 7.300 + 0.082 = 7.382"
10-28-2011, 05:50 PM
#6
this is the method i used
Originally Posted by XtraCajunSS
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!!!
I hope this helps someone. I have explained it so many times I think I do it in my sleep!!!
Shane_______________________________
Originally Posted by XtraCajunSS
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!!!
I hope this helps someone. I have explained it so many times I think I do it in my sleep!!!
Shane_______________________________
Last edited by 99 Blue Bird; 10-28-2011 at 05:56 PM.
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LS CHEVY II (01-04-2021)
10-28-2011, 09:53 PM
#7
If you are getting the correct number of turns on the rocker arm bolt per the method outlined by XtraCajunSS above, and it's the pre-load you want, then it looks right.
However ... since you have LS7 lifters, what have you decided to use for the pre-load? As I mentioned above, their mid-point of travel is around 0.082".
So are the valve stems at different heights between the intake and exhaust valves on our head? Typically, LSx engines use the same length pushrod for both intake and exhaust.
Did you check more than one (or all) intake and one exhaust valve to make sure you weren't seeing some variance? Sometimes there is some slight variance between them, and that is maybe what you're seeing. See this thread ... pretty interesting as this guy seems to have almost 0.040" variance across his motor.
See Post #49 and beyond:
http://forums.corvetteforum.com/c5-t...er-in-car.html
However ... since you have LS7 lifters, what have you decided to use for the pre-load? As I mentioned above, their mid-point of travel is around 0.082".
So are the valve stems at different heights between the intake and exhaust valves on our head? Typically, LSx engines use the same length pushrod for both intake and exhaust.
Did you check more than one (or all) intake and one exhaust valve to make sure you weren't seeing some variance? Sometimes there is some slight variance between them, and that is maybe what you're seeing. See this thread ... pretty interesting as this guy seems to have almost 0.040" variance across his motor.
See Post #49 and beyond:
http://forums.corvetteforum.com/c5-t...er-in-car.html
Last edited by ZeeOSix; 10-28-2011 at 10:02 PM.
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10-28-2011, 10:21 PM
#8
I just checked one cylinder. But to get to .080 preload would be 1.75 turns using shanes method and that was 11.5 turns on the pushrod checker. Which is 7.375. So ill check that out a couple times on different cylinders and see how that works out.
10-29-2011, 03:52 PM
#9
well i checked all drivers side cylinders and 2 from the passenger side using the stock pushrods and the pushrod length checker extended 11.5 turns which is a 7.375 pushrod.
using shanes method of 1 full turn on the rocker bolt after finding 0 lash being .047 preload i was at 1.75 turns to get to 22ft Lbs with a 7.375 pushrod which would put me at .082 preload. so ill be going with a 7.375 pushrod for my motor.
thanks Z for all the help
using shanes method of 1 full turn on the rocker bolt after finding 0 lash being .047 preload i was at 1.75 turns to get to 22ft Lbs with a 7.375 pushrod which would put me at .082 preload. so ill be going with a 7.375 pushrod for my motor.
thanks Z for all the help
10-31-2011, 04:40 PM
#14
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From what I've read you wanna be in about the middle of its range. So if it has a .100 range of movement you wanna be at about .050 preload. I dont know the range of these lifters so no help there. Go!
10-31-2011, 04:47 PM
#15
lol thanks. there is a table in post 4 that shows the travel of LS7 lifters. i just did some searching on here aswell that said anywhere from .050 to .100 preload is acceptable. no more than .100 and GM sets theirs up to .080. so im sticking with .082 preload.
11-01-2011, 12:55 PM
#16
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SmokyRum (07-15-2019)
11-01-2011, 01:17 PM
#17
for sue. thanks for the help.
i think the one major thing that was confusing me was the fact that i was told to use 7.425 pushrods. and i decided to measure just in case. and when my lengths were not even close to 7.425 it was making me think i was doing something way wrong.
i think the one major thing that was confusing me was the fact that i was told to use 7.425 pushrods. and i decided to measure just in case. and when my lengths were not even close to 7.425 it was making me think i was doing something way wrong.
02-12-2017, 02:00 AM
#19
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Alright guys maybe I'm the only one who caught this... your BOLT per turn goes down .050 NOT the lifter. If you have a 10' pole.. the end of it is stationary (valve side of rocker) You go out from the stationary end to the middle @5' you pull down 2', what did the non stationary end do? It went down 4'!!! IF YOUR GETTING A TURN AND A HALF ON THE BOLT, THATS .075 THE BOLT which equals .1275 on the lifter!!! Your suppose to multiply that figure times 1.7!!! Each turn of .050 on the bolt is .078 on the lifter
Last edited by Gtslo04; 02-12-2017 at 02:05 AM. Reason: Misinformation
02-12-2017, 07:19 AM
#20
Alright guys maybe I'm the only one who caught this... your BOLT per turn goes down .050 NOT the lifter. If you have a 10' pole.. the end of it is stationary (valve side of rocker) You go out from the stationary end to the middle @5' you pull down 2', what did the non stationary end do? It went down 4'!!! IF YOUR GETTING A TURN AND A HALF ON THE BOLT, THATS .075 THE BOLT which equals .1275 on the lifter!!! Your suppose to multiply that figure times 1.7!!! Each turn of .050 on the bolt is .078 on the lifter