themack56

iTrader: (70)

well im asking cause im running the stock size 7.4 pushrods on my head and cam ls1 and i just now found out i needed 7.425s. Is there a power loss? if so how much ? any potential problems in the long run?

ive been running like this for like 2000 miles

vsocks1

iTrader: (6)

How did you determine what is needed, did you measure?
What lifters are you using and what preload are you going for?

More info needed!

themack56

iTrader: (70)

i used stock ls6 lifters, i asked on here what pr s i needed and some guy said stock size, but come to fine out everyone running the cam is running 7.425s

MrElectric03

iTrader: (71)

Nobody can say "You need these pushrods with this cam" unless they have measured the pushrod length with the motor assembled.

Ive been told that .080" is ideal preload, if you have that or within .010" of it I think you are ok.

MrElectric03

iTrader: (71)

Get one of your rockers at the top of the stroke, turn the motor while watching the rockers, find one that goes up as yuo turn and when it stop use that one. Now loosen it a little bit, tighten it while moving the rocker up and and down with your hand, and get it to where it just stops rocking back and fourth. Now mark your bolt and tighten it to 22 ft. lbs. Count how many turns it takes, each turn is worth .050", so you should get a little over 1.5 turns or close.

SOMbitch

iTrader: (8)

Huh? what am I missing This is not setting lifter preload but torqueing rockers......

Search Vettenuts for the best post descibing how to set lifter preload.

If your valvetrain is not excessivly loud you are prolly ok though.....

MrElectric03

iTrader: (71)

I dont like this method but it doesnt require a pushrod length tool so I thought I would suggest it.

For sure hit up vettenuts, he helped me out with my valvetrain issues I had.

SUCK MY SS

iTrader: (14)

have the heads been milled? stock thickness head gasket?

a quick and easy check for you is to loosen 1 IN & EX rocker... use a sharpie and color in the tip of each of the two valves... bring the rockers down to zero lash and notate how many turns it takes to torque the rocker bolt to 22lb ft... like electric said, each full turn is approximately .050... now rotate the engine two complete turns...loosen the two rockers of the valves you marked... look at the imprint left from the rocker tip to the valve tip... it should be close to square in the middle... never coming close or off of the valve tip...unless you milled a lot off the heads you should be in a fairly safe zone with the 7.400 pushrod and a ground base cam...
your preload will be fine anywhere from .06 to .10, but ideally you will want to be between .075- .085... most importantly you want a clean centered contact patch on the valve tip with proper preload to match

vettenuts

iTrader: (4)

I don't like this method either but it might give the OP an initial indication. The only correction I would add is that the turns measured should be corrected for the rocker ratio. Each turn is 1.25 mm or 0.050" but this is at the bolt (pivot point of the rocker). To correct for movement at the pushrod you need to multiply this by 2.7/1.7 or 1.588 (parallel triangles). So for 1.5 turns you would get:

1.5 X (1.25/25.4) X (2.7/1.7) = 0.117" of preload at the pushrod.

willyfastz

Internet math sucks for building engines. If the op wants to actually have the correct length pushrods he'll need to purchase an adjustable pushrod. Which he can get for around $20 new. Then simply measure and add the desired preload (I wouldn't recommend over .050").

Internet math isn't going to get him anything but a bunch of guesses at what the engine actually wants.

SUCK MY SS

iTrader: (14)

.05 preload is not enough for an oem lifter in any sort of performance application wanting to spin the engine higher than stock

jmm98LS1

iTrader: (28)

I ran 7.4" pushrods with the ASA cam for 3 years, no problems & quiet valvetrain.

TooLateVTEC

iTrader: (2)

If the lifters are making a good amount of noise than its probably ok.

If your real worried about it, buy a push rod length checker and check it...its the right thing to do.

dre2013

iTrader: (7)

i have a set of 7.425's for sale...too long for my setup. $90 shipped

vettenuts

iTrader: (4)

I don't disagree at all, but the calcs will ball park it until he has the tool. Anyone buying a cam should be buying an adjustable pushrod as part of the installation kit, period. The vendors should sell the cams with the tool and no pushrods, that would force the issue.