How do you measure preload to determine pushrod length?
04-07-2007, 03:53 PM
#1
Moderator
Thread Starter
iTrader: (4)
Join Date: Nov 2003
Location: Plainfield, CT
Posts: 10,520
Likes: 0
Received 0 Likes
on
0 Posts
How do you measure preload to determine pushrod length? Just what the question says. I have a TR224 cam and am adding AFR 205's milled .030 with a stock GM gasket & new LS7 lifters. I need to find out what size pushrods I need. How do you measure preload?
04-07-2007, 05:19 PM
#2
You need to have the cam in the right postion. Crank the motor over by hand until you see the exaust valve open and close then the intake open and close. Then stop. You can go a few degrees past closed on the intake.
Take a black marker and color the valve stem. I use the #2 cylinder because its easy to get to and see.
Set the rocker and pushrod in place. How many turns before the rocker sits flush and you feel you need to use torque wrench to hit 22 ft lbs. You want to know how much "crush" you have. How many turns to seat the rocker onto the pedestal. Then go ahead and torque it to 22 ft lbs.
Then crank the motor over by hand so you get about 3-4 cycles on the cylinder your using. Then take the rocker off and look at the valve stem. The marker should be worn off the valve stem. Where is the wear?
Report your results. How many turns and where is the pattern on the valve stem.
Take a black marker and color the valve stem. I use the #2 cylinder because its easy to get to and see.
Set the rocker and pushrod in place. How many turns before the rocker sits flush and you feel you need to use torque wrench to hit 22 ft lbs. You want to know how much "crush" you have. How many turns to seat the rocker onto the pedestal. Then go ahead and torque it to 22 ft lbs.
Then crank the motor over by hand so you get about 3-4 cycles on the cylinder your using. Then take the rocker off and look at the valve stem. The marker should be worn off the valve stem. Where is the wear?
Report your results. How many turns and where is the pattern on the valve stem.
04-08-2007, 12:37 PM
#5
TECH Senior Member
iTrader: (23)
Join Date: Aug 2005
Location: Watertown, NY
Posts: 8,797
Likes: 0
Received 0 Likes
on
0 Posts
Originally Posted by davered00ss
Just what the question says. I have a TR224 cam and am adding AFR 205's milled .030 with a stock GM gasket & new LS7 lifters. I need to find out what size pushrods I need. How do you measure preload?
04-08-2007, 04:15 PM
#6
TECH Veteran
iTrader: (14)
Join Date: Apr 2005
Location: N. Falmouth MA
Posts: 4,085
Likes: 0
Received 0 Likes
on
0 Posts
Originally Posted by 99blancoSS
You need to have the cam in the right postion. Crank the motor over by hand until you see the exaust valve open and close then the intake open and close. Then stop. You can go a few degrees past closed on the intake.
Take a black marker and color the valve stem. I use the #2 cylinder because its easy to get to and see.
Set the rocker and pushrod in place. How many turns before the rocker sits flush and you feel you need to use torque wrench to hit 22 ft lbs. You want to know how much "crush" you have. How many turns to seat the rocker onto the pedestal. Then go ahead and torque it to 22 ft lbs.
Then crank the motor over by hand so you get about 3-4 cycles on the cylinder your using. Then take the rocker off and look at the valve stem. The marker should be worn off the valve stem. Where is the wear?
Report your results. How many turns and where is the pattern on the valve stem.
Take a black marker and color the valve stem. I use the #2 cylinder because its easy to get to and see.
Set the rocker and pushrod in place. How many turns before the rocker sits flush and you feel you need to use torque wrench to hit 22 ft lbs. You want to know how much "crush" you have. How many turns to seat the rocker onto the pedestal. Then go ahead and torque it to 22 ft lbs.
Then crank the motor over by hand so you get about 3-4 cycles on the cylinder your using. Then take the rocker off and look at the valve stem. The marker should be worn off the valve stem. Where is the wear?
Report your results. How many turns and where is the pattern on the valve stem.
W/ the PRLC, on a dry lifter, it's a delicate procedure. I started the PRLC adjusted to 7.300. Then I turned it until I felt it stop. DON'T force it! I used just a light touch of my finger tips to turn the PRLC. I ended up w/ 7.300 after a couple tries and rechecks (w/out adding preload of .050"). -On -=Modified=-'s car.
