Proper way to use a pushrod length checker?
06-25-2007, 10:56 AM
#2
Make sure the lifter is on the base circle of the cam (valve closed). Adjust length of pushrod to about 1/8" shorter than stock. Install in pushrod hole to be checked. Put on your rocker arm guide (the aluminum bar) and then install a couple of rockers including the one you are checking and tighten rockers snug (no need to fully torque them down). Gently push rocker nose against the valve stem and then rotate the pushrod to just take out the clearance. You may need to remove the rocker to do this and then repeat step. Once you have the pushrod length so it just takes out the clearance, remove the rocker and the pushrod without turning it. Now count the number of turns it takes to get the pushrod back to fully closed (there should be two white lines that line up at each rotation). Then figure out the length. For example, for the Comp cam adjustable pushrod, the base length is 6.800" and each turn is 0.050". So if you had 10.5 turns you would have:
6.800 + 10.5 X 0.050 = 7.325
This is the length without preload for the lifter. Now add in the desired preload. If you want 0.100" of lifter preload, you end up with a 7.425" pushrod.
Don't measure the pushrod length with a vernier, the actual measurement is gauge length that you use to order the pushrods and that is what the pushrod is designed to measure. Check at least one intake and one exhaust.
6.800 + 10.5 X 0.050 = 7.325
This is the length without preload for the lifter. Now add in the desired preload. If you want 0.100" of lifter preload, you end up with a 7.425" pushrod.
Don't measure the pushrod length with a vernier, the actual measurement is gauge length that you use to order the pushrods and that is what the pushrod is designed to measure. Check at least one intake and one exhaust.