How to use PR length checker
05-26-2009, 11:44 PM
#1
How to use PR length checker Thats pretty much the question, How do factor the lifter pre load and what exactly is that? I will be insalling the H/C setup in my sig along with LS7 lifters and want to be sure i get the correct length PRs. All help would be appreciated.
05-27-2009, 07:23 AM
#2
In a nut shell... You need to know what preload you want to run. I think the LS7 lifters are higher than the LS1 lifters... over .100...?? Do a search on "lifter preload"... lots of threads.
Anyway, you install the lifter, pushrod checker set shorter than you need, rocker and torque the rocker down. You lengthen the pushrod checker until you reach zero lash. That is...just until all the slack is taken up, and you feel resistance while spinning the checker. Also you wont have clicks when you "rock" the rocker back and forth.
At this point, you need to know the length of the pushrod checker. You can either take it out and measure it, or you use the indicator marks on the tool and count the revolutions. I usually do both...to doublt check.
Once you know the length of the checker at zero lash, you add your desired preload measurement. So lets say for argument sake your LS7 lifters require .100" of preload. Then your checker measures out to 7.300". You want to order 7.400" push rods.
Like I said...thats the basic jist. I just did a pushrod swap to a different length on my car to see if I could quiet a tick...and I can tell ya there are a good number of threads on pushrod length and preload floating around.
J.
Anyway, you install the lifter, pushrod checker set shorter than you need, rocker and torque the rocker down. You lengthen the pushrod checker until you reach zero lash. That is...just until all the slack is taken up, and you feel resistance while spinning the checker. Also you wont have clicks when you "rock" the rocker back and forth.
At this point, you need to know the length of the pushrod checker. You can either take it out and measure it, or you use the indicator marks on the tool and count the revolutions. I usually do both...to doublt check.
Once you know the length of the checker at zero lash, you add your desired preload measurement. So lets say for argument sake your LS7 lifters require .100" of preload. Then your checker measures out to 7.300". You want to order 7.400" push rods.
Like I said...thats the basic jist. I just did a pushrod swap to a different length on my car to see if I could quiet a tick...and I can tell ya there are a good number of threads on pushrod length and preload floating around.
J.
