I'm currently having some issues with a engine I'm building. Forged rod/piston LS3 with LS3 heads. The lifter pre-load seems to be all over the place. I measured each one several times and got the same numbers.

A little info on engine
Forged rod/Piston LS3 with LS3 heads
Stock rocker arms with CHE bronze trunion upgrade, new GM rocker stands
Johnson 2116LSR link bar lifters (box says .035" pre-load)
BTR stage IV PDS camshaft
ARP studs and LS9 head gaskets
LSA supercharger setup

I know there are a few different ways of checking pre-load. I had no luck with the pushrod length checker tools. I've also been told that 1 full bolt turn is around .086"-.088" pre-load so most of mine were right around 1/4 turn from zero lash to 22ft lbs. What I actually did was mount a dial indicator up and measure off the top of the rocker and set to zero, and loosen the rocker till it comes up to zero lash and I got my measurement. It always went to zero when torqued back to 22ft lbs. So here is what I ended up with. I used a BTR .080" wall 7.525" pushrod to get all of these measurements.

1. Intake .033" Exhaust .029"
3. Intake .021" Exhaust .022"
5. Intake .025" Exhaust .022
7. Intake .024" Exhaust .024

2. Intake .021" Exhaust .018"
4. Intake .020" Exhaust .012
6. Intake .019" Exhaust .009"
8. Intake .022" Exhaust .016"

I need to go back and remeasure all of them because I bought a new solid arm base and it changed the measurement on a couple that I checked again. The indicator I borrowed had some flex to it so it wasn't accurate. I checked a couple others with the new setup and found they come out around .002-.003" more. I remeasured #6 exhaust side and got .012" instead of .009". I thought with that particular one there may be something wrong with the rocker arm so I installed a stock bearing rocker arm and measured pre-load to now be .017". That is a .005" increase over the rockers with the CHE trunions in them. I swapped out a couple others and found the same, measurement increased with the stock rocker. So is there really that much play in the floating design of the CHE rocker bushings? Also is it pretty typical to have that amount of pre-load variance with the Johnson 2116LSR lifters?

 

It's not the lifters, its the valves....you will have to use different length custom push rods, or shim the pedestals, or go to an adjustable rocker arm setup.

 

It looks like you're measuring it correctly by the pictures. However, one BIG caution is to make sure the indicator travel is directly in-line with the movement of the rocker. Meaning if the tip of the indicator moves front-back during the measurement, your reading WILL be off. The indicator tip should be centered to the pivot point (front-back).

The best way really is to use a adjustable pushrod.

I use a feeler gage stack between the rocker tip and valve tip. To know what thickness of shims you should use multiply the desired preload amount by the rocker ratio (.035" x 1.7:1 = .0595" shim). Then you can adjust the pushrod to "zero lash" and measure each cylinder/lifter individually and see what the best size(s) may be.

If your heads and/or block were decked and there is a little taper/tilt/cant to any of the surfaces, this will effect the pushrod length/preload when using the same length tool for each lifter.

As far as the bushings effecting the preload, most likely not. The ID and OD are held within .0001". Feel the difference between a stock rocker and a CHE bushing rocker and you will notice how much less "slop" there is in the CHE style.


Good luck,
Cole

 

The pushrod length checker works if used properly. Here is a link to how Katech shows the process. I followed their method and after a season of racing, I inspected everything and noticed the rocker tip was making contact in the center of the valve tip, so the measuring process was successful.

 

I use an extension on the dial indicator and don't put the tip on it, this way I have more room to get to the bolt head and the flat end without the tip can't fall in the oil hole to mess up the measurement. I torque them down and zero the indicator as some lifters bleed down slow, but all let out well and your measurement is when it stops going out.