Lifter Preload How-To

[juice12ufo]

To clear up some confusion about lifter preload on cam swaps, I have put together a little tutorial. This IMHO is the most accurate and comprehensive way to verify/adjust lifter preload.

First, make sure that the lifter that you will be testing is on the cam base circle. I like to just rotate the crank and watch the rocker. When the rocker comes off its lobe, you will see it. I give it a little crank more after it comes of the lobe to make certain it is completely on the base circle.

Next, take off the rocker arm. To check multiple pushrod lengths, you will need to get yourself a pushrod length checker. Start with stock length (7.400) and slide it into the pushrod hole:


Then put the rocker arm back on, but leave it nice and loose. You need to tighten the rocker down just to zero lash. So, grab the spring end of the rocker arm and wiggle it towards and away from the valve stem as you tighten down the rocker arm. Tighten the bolt until the rocker will no longer wiggle away from the valve stem, and no further!!!

Now, you need to set up your dial indicator. This is how I set mine up. Get it set on the lifter side of the rocker. Try to mimic the angle of the pushrod best you can. I had to offset mine a bit to get the socket in there. Zero out the dial indicator like in the picture.




Now, your baseline is zero lash, zero preload. Now torque your rocker arm bolt to 22 ft-lbs. You dial indicator will not respond immediately. Your lifter will now bleed off slowly. Just watch the dial indicator move. Eventually it will slow down and stop. This is your lifter preload!
In this picture, my lifter preload is .080". Right where I want it.


To verify an accurate measurement, untorque your rocker back to zero lash and verify that the indicator falls back to zero. If it doesn't, your indicator moved in the process, and you need to do it again.

Repeat these steps with different lengths on your adjustable pushrod to get what you want. I then mark the tops of the valve stems to verify proper rocker sweep. You want to get the best of both worlds here. Get a nice centered rocker sweep and preload within the acceptable boundaries and you are good to go. It may take a few sessions of trial and error with lengths, but you'll get it right eventually. I suggest .025" increments for length.