Blu99T/A

iTrader: (5)

I have read virtually every thread on tech in regards to pushrod length over the last few days and still have questions.

Here is my setup:
370 LQ4 block
From Pred Z: CAM: COMP CAMS CUSTOM GRIND (DEGREED UPON INSTALLATION)
• 230/232 .613/.595 LSA111
• GRIND# LS1 3016/3726 HR111.0
HEADS: PRC 220cc 5.3L Stage 2.5 CNC Ported Heads 57CC
Never been milled, they are just as they came from Texas Speed.
VALVE SPRINGS: PRC DUAL GOLDS
• 2.02 INTAKE/1.575 EXHAUST VALVE SIZE
PUSHRODS: COMP CAMS
• 7.4 Comp Cams PR
Stock rockers
LS7 lifters

The issue I am having is the valvetrain is exremely noisy with my new motor, so I assumed the PR were too short.
I got the Comp Cam pushrod length checker and came up with this:

9.5 turns
6.8+9.5x.050=7.275
Add preload of .075=7.35

The math adds up, but I am confused at how my 7.4 pushrods are too long.
With my 7.4's I am measuring .125 preload, which I believe is way too much, would this be causing the noise?

Am I missing anything?

Greekey

iTrader: (3)

You have 57cc chambers, a different cam, ls7 lifters, and your still using 7.4 pushrods? They are to long, not to short. Are you measuring for pushrods with the pushrod length checker on the base circle of the cam?

Blu99T/A

iTrader: (5)

Yep, #1 Cyl on TDP.
Barely any miles on this motor.

Greekey

iTrader: (3)

Your pushrods are to long and your preload is crazy. I might be wrong but that preload I've never heard of anyone running. You should be running a 7.350 pushrod like you already measured for.

Blu99T/A

iTrader: (5)

I think GM calls for no more than .120

Greekey

iTrader: (3)

What head gasket are you using?

Blu99T/A

iTrader: (5)

Gm mls

Greekey

iTrader: (3)

I just think their to long man. Hopefully someone else will chime in.

Blu99T/A

iTrader: (5)

I measured quite a few times and even turned the motor over twice to TDC and remeasured and keep getting the same measurements.

Greekey

iTrader: (3)

Are you sure your not getting 8.5 turns? I have a similar setup, and got 8.5 turns. Not saying your dumb, but I screwed up on this as well 2 weeks ago. Are you also using a 6.8 closed and a 7.8 open pushrod length checker?

99Bluz28

iTrader: (35)

You did use some Valvetrain Checking Springs, correct?
I had to go with longer PR's 7.450", to bring the preload up to .059", and I have only a little increase in valvetrain noise, and my lift is a hair more at, .614" int./.617" exh..

blackmagicturbo

iTrader: (2)

I just went through the same thing with my motor and ordered 7.375 through Trend (Sasho) he helped me through it with my non adjustable roller set-up ,, key is to adjust the push-rod checker until you can pre-load the lifter 1 full turn to seat 22 pounds torque ,11 1/2 turns on mine with a .040 washer under my rocker stands to correct my geometry...it took me a few trys but i finally got it ,, i ordered 7.400 the first time, boy was i off ... call them up they will walk you through it ,, (11 .5 turns x .050 a turn)= .575 + 6.800 = 7.375 hope this helps..

Blu99T/A

iTrader: (5)

Yeah, I am using the Comp Cams Adj. Pushrod Length Checker that is 6.8 long.
At 9.5 turns, it is snug against the rocker, not tight.

osuhog

iTrader: (16)

Your pushrods are too long. I measured wrong when I first did my cam swap & had trouble too. I only found out when I went to the dyno & had a drop in power from bolt-ons. Tuner said he thought my pushrods were too long & hangling valves open not building compression.

So, I took it home, removed & measured pushrod preload again. Sure enough, my preload was .125 with my 7.425 pushrods. I ordered some 7.375 to get me back down to .075 preload, installed them, took it back to the dyno, & everything was golden.

Again, .125 is way too much preload.

I don't completely understand though why you knowingly went with 7.4" pushrods for .125 preload? You need 7.35" pushrods. Looks to me like you measured everything correctly, but just went with the wrong size pushrods.

Blu99T/A

iTrader: (5)

I did not knowingly go for .125 preload, that was a mistake on my part from when I originally out it together.

Blu99T/A

iTrader: (5)

A buddy of mine has some Comp 7.35's that I am going to throw in and see how it does.
Should have it all swapped out this weekend and will report back.

3zman

I just went through this and I do it in a slightly different way in that I have difficulty with the adjustable pushrod method. I bought some .047, .020, and 0.010 shims from McMaster-Carr. I started off with a 7.35 pushrod and put enough shim under the rocker (HS 1.8's) to where the rocker and the valve tip had play. I then used a feeler gauge to determine the gap (roller tip and valve stem). I substracted out the amount of shim to get the preload I wanted, in this case 0.050. I marked the valve tip with layout die and re-assembled the rocker with preload. I turned the motor over and verified that the geometry was good (wear mark in the center of the valve tip).

Blu99T/A

iTrader: (5)

The 7.350 helped quite a bit with the noise (sewing machine sound), still noticable with the hood shut, but only if you listen for it. My neighbor didn't hear it until I pointed it out.

I am assuming that the cam is noisy at this point with its aggressive lobes. Probably going to be as good as it gets.

blackmagicturbo

iTrader: (2)

good to hear you fixed it !

soundengineer

iTrader: (16)

when on the base circle of the cam, take a rocker bolt and get it to zero lash(just where the pushrod starts to grab and no longer turns freely)
then count the # of rocker bolt turns to 22ft-lbs...
each full rotation is .047 preload.