Question about Pushrod Length
Question about Pushrod Length Ok so it is my first time measuring for pushrods (except for the rocker bolt turn technique) and i'm trying to confirm if I did it right.
Set-up:
PRC LS6 heads milled .020, stock LS1 headgasket and Lunati street lifters which are supposed to be .050 taller than stock lifter and SNL V2 cam.
here is what I did:
Put the cylinder to TDC (heads were off so confirmed this by sight). installed CC adjustable pushrod and by guess and check to get the PR close to zero lash. installed the rocker arm and torqued it to 22ft lbs and then adjusting the adjustable pushrod with my fingers until the rocker is just snug and the play is gone. Then removed pushrod and measured. Got a length of 7.245 at zero lash and then added .030 for preload giving me an overall length of 7.275. This seems short to me. If someone who has some experience with this could post up if this length seem realistic or if I messed something up somewhere. Thanks.
Set-up:
PRC LS6 heads milled .020, stock LS1 headgasket and Lunati street lifters which are supposed to be .050 taller than stock lifter and SNL V2 cam.
here is what I did:
Put the cylinder to TDC (heads were off so confirmed this by sight). installed CC adjustable pushrod and by guess and check to get the PR close to zero lash. installed the rocker arm and torqued it to 22ft lbs and then adjusting the adjustable pushrod with my fingers until the rocker is just snug and the play is gone. Then removed pushrod and measured. Got a length of 7.245 at zero lash and then added .030 for preload giving me an overall length of 7.275. This seems short to me. If someone who has some experience with this could post up if this length seem realistic or if I messed something up somewhere. Thanks.
TECH Regular
Joined: Jul 2011
Posts: 452
Likes: 2
Ok so it is my first time measuring for pushrods (except for the rocker bolt turn technique) and i'm trying to confirm if I did it right.
Set-up:
PRC LS6 heads milled .020, stock LS1 headgasket and Lunati street lifters which are supposed to be .050 taller than stock lifter and SNL V2 cam.
here is what I did:
Put the cylinder to TDC (heads were off so confirmed this by sight). installed CC adjustable pushrod and by guess and check to get the PR close to zero lash. installed the rocker arm and torqued it to 22ft lbs and then adjusting the adjustable pushrod with my fingers until the rocker is just snug and the play is gone. Then removed pushrod and measured. Got a length of 7.245 at zero lash and then added .030 for preload giving me an overall length of 7.275. This seems short to me. If someone who has some experience with this could post up if this length seem realistic or if I messed something up somewhere. Thanks.
Set-up:
PRC LS6 heads milled .020, stock LS1 headgasket and Lunati street lifters which are supposed to be .050 taller than stock lifter and SNL V2 cam.
here is what I did:
Put the cylinder to TDC (heads were off so confirmed this by sight). installed CC adjustable pushrod and by guess and check to get the PR close to zero lash. installed the rocker arm and torqued it to 22ft lbs and then adjusting the adjustable pushrod with my fingers until the rocker is just snug and the play is gone. Then removed pushrod and measured. Got a length of 7.245 at zero lash and then added .030 for preload giving me an overall length of 7.275. This seems short to me. If someone who has some experience with this could post up if this length seem realistic or if I messed something up somewhere. Thanks.
Also, having the piston on TDC on the compression stroke might not give you a perfect base circle poison. You should use the EO/IC method to position the lifter for this measurement. Do a search on pushrod length ... there's about 100 threads lately about it all.
How did you measure the adjustable pushrod after you got the length to zero lash. As an example, it should be something like 6.800" + (0.050" x No. of turns). So if you had 11 turns, it would be 6.800 + (0.050 x 11) = 6.800 + 0.550 = 7.350". You have to know how many turns it took on the adjustable pushrod to get your zero lash length - then add the amount of lifter pre-load you want based on the lifters you are using.
Also, why only 0.030" lifter pre-load? Sounds way too little to me. Which lifters do you have? See attached photo. Lifter pre-load depends on what the total plunger travel is for the lifters you have.
I had both heads off. I set the cylinder to TDC so both lifters were on the basecircle indicating the power stroke and the valves would both be closed. I then installed both heads and performed the measurement.
Lifters are the Lunati street lifters. they advise preload between .030 and .050.
I have searched quite a bit, and I guess I just wanted a second opinion on the measurement as it seemed short to me. ill turn the motor to open the exhaust valve and measure the intake and see if I get the same reading... I was actually just about to try that.
I measured the adjustable pushrod by turns and confirmed it by measuring the threaded area with a digital caliper. I came up with just under 9 turns of the pushrod X.050= .450 + 6.800 = 7.250 + .030 = 7.280. I then used the digital caliper and the opening measured at .445 which given the calculations above would put me at 7.275. So even with a .050 preload that would still put me at 7.3 which still seems a bit short.
Thanks.
Lifters are the Lunati street lifters. they advise preload between .030 and .050.
I have searched quite a bit, and I guess I just wanted a second opinion on the measurement as it seemed short to me. ill turn the motor to open the exhaust valve and measure the intake and see if I get the same reading... I was actually just about to try that.
I measured the adjustable pushrod by turns and confirmed it by measuring the threaded area with a digital caliper. I came up with just under 9 turns of the pushrod X.050= .450 + 6.800 = 7.250 + .030 = 7.280. I then used the digital caliper and the opening measured at .445 which given the calculations above would put me at 7.275. So even with a .050 preload that would still put me at 7.3 which still seems a bit short.
Thanks.
TECH Regular
Joined: Jul 2011
Posts: 452
Likes: 2
Sounds like you're doing it right ... but yes, rconfirm using the EO/IC method to ensure lifter is near center point of the base circle.
Those Lunati lifters must be the big difference causing your shorter measurements. Contact Lunati tech dept if they have one and confirm (for peace of mind) if those lifters are shorter than GM lifters.
Those Lunati lifters must be the big difference causing your shorter measurements. Contact Lunati tech dept if they have one and confirm (for peace of mind) if those lifters are shorter than GM lifters.
Sounds like you're doing it right ... but yes, rconfirm using the EO/IC method to ensure lifter is near center point of the base circle.
Those Lunati lifters must be the big difference causing your shorter measurements. Contact Lunati tech dept if they have one and confirm (for peace of mind) if those lifters are shorter than GM lifters.
Those Lunati lifters must be the big difference causing your shorter measurements. Contact Lunati tech dept if they have one and confirm (for peace of mind) if those lifters are shorter than GM lifters.
any way thanks for the help
