82cecil

Crank at TDC

stock 317 head w/ upgraded springs

.051 MLS gasket

EPS 226/234 cam w/ 7.425 push rod, new LS-7 lifters

set rocker to touch valve tip without play then begin to measure how far it takes to reach 22ft lb.

not sure I even have a problem, but most threads/posts I ve searched need more than just under 1/2 turn to get the 22ft lb torque required.

Is there a problem?

thanks

Cody Strife

iTrader: (1)

I was thinking anywhere between 1 turn to 1 1/2 turns from zero lash to 22 ft lbs of torque was fine.

I prefer pushrod measuring tool myself.

Way2Fast

iTrader: (1)

Every 1/2 turn past zero lash is about .025 of lifter preload. Sounds like your pushrod is too long.

82cecil

what a person calls zero lash can make a big difference, according to how much play is zero to me vs another, or how much force is used to before the push rod no long rotates.

if I back the bolt out to where the rocker is touching with out "free play", (rocker bolt all the way down but not snug) I can get about 1 1/2 to almost 2 turns to 22ft lbs.


Using the method in the 6.0 manual, I noticed in this effort is that the no.1 intake lifter does not compress as easy as the no.1 exhaust. No. 3 intake is the same as no.1. this concerns me also.

vettenuts

iTrader: (4)

Actually, until the rocker bottoms and there is no additional preload applied, each turn is more like 0.038" of preload.

3rdCoastPowerSports

iTrader: (5)

I have found the counting turns method to be inaccurate. use an adjustable push rod and feeler gauges to find your zero lash measurement. Then simply add your desired amount of preload and order up the closest size pushrods.

badazz81z28

iTrader: (6)

Hmmm..Most threads I see says to measure for pushrods.

Thats 1/4" this...1/4 that....is just a crap shoot!. Get the tool, measure.

msydow

i have only had to measure for pushrods twice and i bought the tool the first time. most vendors can have you the right pushrods in two days anyways.

soundengineer

iTrader: (16)

Rocker Bolts have a 1.25 pitch
which means 1 full turn = 0.0492 preload

Ideal preload is actually somewhere between .020 and .040

so you are at roughly .020

which is fine.....

if you are worried about it, then you can buy a shorter pushrod

this is also assuming you are at a point on the cam where the valve would be closed

badazz81z28

iTrader: (6)

I'm pretty certain GM spec for LS7 lifter is more than that.

.050-.080"....Some say .100"

soundengineer

iTrader: (16)

for the stock cam.....yes




aftermarket cam, .020 to .040

soundengineer

iTrader: (16)

also, the base circle on the EPS cam doesnt have enough difference from the stock cam journal to warrant a change in pushrod length...
a 7.400 pushrod would give you that extra preload you were looking for
7.400 pushrod would put you at .045 preload

badazz81z28

iTrader: (6)

Whats the difference?

3rdCoastPowerSports

iTrader: (5)

can you back this up with any publications (cite)?

soundengineer

iTrader: (16)

materials its made of, shape of the lobe
you can cause a lifter to basically collapse partially because of the aggressive lobes, which means you need extra travel to allow for that lobe and the new faster rate of travel...

put in a good lifter, and you dont have to worry about that as much


from a few of the cam grinders....optimum around .030
the ranges they say to be within that are still ok..
Cam Motion says .020~.060
Comp Cams says .020~.070
Lunati says .020~.060

most pro level engine builder will tell you .020~.040

they say this for both stability and cam lobe life

badazz81z28

iTrader: (6)

My Comp Cam (TSP) instructions do not mention anything about lifter pre-load. I would assume it has to do with the lifter type...I don't know...any else want to chime in on this one?

soundengineer

iTrader: (16)

http://www.compcams.com/v002/Pages/4...icVsMechanical


Says .020~.070 for hydraulic
Also says 1/4 to 3/4 turn

BKsNHRA

iTrader: (4)

I use the eps 226-230 cam. 7.4 pr where to short. Noisy as hell. 7.425 made it quiet. This is on stock lifters. I gettin ready to change lifters to ls7 because one of my stock ones failed. I don't know what the preload would be for a ls7 lifter because their not in yet.

soundengineer

iTrader: (16)

like I said previous....020 preload is just fine....and as you see.. your valvetrain is less noisy with the lesser amount of preload


Posted from LS1Tech.com App for Android

Darkman

iTrader: (2)

The 1/4 to 3/4 turn referred to is for the adjustment screw on adjustable rockers and not for the rocker bolt for non-adjustable rockers.