Adjusting Comp R's with a Compression Tester
 

Okay this may sound really weird but it really seemed to work for me. I have tried several times to get the Comp r lifters and pro mag rockers dialed in correctly. I followed Comps directions to a T at .02 to .04 @ TDC and they were off. I tried a dial indicator and set to .10 preload @ TDC and still off. I tried .20 @ TDC still no good. Until...


Doing a compression test I found the cyl to be the following,
1 170 2 165
3 170 4 165
5 180 6 160
7 180 8 160

While adjusting the lifters and seeing the compression go up and level out. Most were 1/2 to 5/8 turn past 0 lash. Here is what I ended up with,
1 185 2 195
3 200 4 195
5 195 6 195
7 195 8 185


Also there was a Major increase in oil pressure. Cold start went from 55 to 75, running warm went from 30 to 45, and warm run in drive went from 22 to 30. Now the car is running very strong. I'll see what the track brings on Thursday.

I thought the preload had to do more with proper valvetrain geometry than cylinder compression.... maybe I'm just not understanding the theory behind this... can anyone offer an explanation?

preload
 

If the preload is not set correctly the valves can hang open and bleed off compression. The pushrod length will determine proper geometry by having the rocker sit dead center with the valve stem.

So the preload is simply adjusting the pressure exerted on the valve seat by the spring... and in adjusting the preload by compression, that's simply checking to make sure the valves aren't hanging open... What about accounting for not enough preload?

???
 

when I was adjusting preload (the depth the pushrod extends into the lifter) I did it with an adjustable rocker arm (Comp pro Mags). The adjusting nut on top of the rocker arm as it is torqued down pushes the pushrod into the lifter.
To much preload can cause the valves to hang open. To little preload can cause a very noisy valvetrain.

that's what I thought, I think we just said it in two different ways

[QUOTE=Taphee6]I followed Comps directions to a T at .02 to .04 @ TDC and they were off. I tried a dial indicator and set to .10 preload @ TDC and still off. I tried .20 @ TDC still no good. Until...

The problem is in your translation of the instructions. The valve lash for them is .002- .004 not .02-.04 that's ten times as much as spec'd by comp.
.100 -.200 is 25 to 50 times the spec.

I have the same set up and I went 1/8 turn past 0 lash. I've set them once and never looked back.
good luck,

Its different on every motor. I set mine to 1/4 turn past 0 lash and have not looked back. On my fieinds car I started off with 1/4 turn and it was hangin valves on 3 cylinders. His wanted 1/8 of a turn past 0 lash.
I did not have a compression tester at the time.
I ended up adjusting the rockers and before putting the valve covers back on I spun it over with the starter. Whe it got a nice even crank thats when I knew it was makin pressure in all 8.
Good Idea with the compression tester.



Brad