mannyman84

iTrader: (2)

So I just finished installing my cam, and heads. Now... I have some 7.4 rods that I bought used with the cam. Guy was running this setup with his Camaro. My question is: at around what preload would this put me in?

Ms3 cam 243's. Resurfaced very little. About the size of a nail. Should I be ok?I don't want to much preload, don't want to bent a rod. I've been reading and .091 seems to be where u want to be. I want to get a pushrod length checker but sometimes I'm impatient. :/

LilJayV10

iTrader: (39)

The only way you are going to know for sure is to check it. You don't have to have an adjustable pushrod checker either.

https://ls1tech.com/forums/generatio...questions.html

Being impatient and working on engines can lead to negative side effects.

baxsom

iTrader: (6)

what lifters?

01ssreda4

iTrader: (96)

Measure....

ZeeOSix

That's what I was wondering also. The pre-load really depends on exactly what lifter you're using, and what the total plunger travel is in that specific lifter. 0.090" may be be too much pre-load for certain lifters.

mannyman84

iTrader: (2)

Sorry. Ls7

mannyman84

iTrader: (2)

I installed the rockets and rods today and turned it by hand and seemed ok. Took them off again and checked push rods and they didn't seem bent, nor did the springs close all the way.

LilJayV10

iTrader: (39)

What were you trying to accomplish by this?

z99ls1

iTrader: (12)

I'm confused. Are you happy because you put them all in and they didn't come out bent? You need to check for the right pushrod length by getting zero lash and than count how many turns it takes tell you reach 22ft lbs. It should be around 1&1/4-1&3/4. I'm not really getting what your trying to say in this post though? Here is a good source on how to find out what pushrod length you need.


Originally Posted by XtraCajunSS
FWIW, EVERY cam install I have done using the LS7 lifter with a cam with greater than .600" lift (read smaller base circle) AND stock heads w/GM MLS gaskets has taken 7.425" pushrods for ~.050"-.060" preload. We measure lifter preload on each and every cam install we do. I have never had a lifter failure nor do we end up with the dreaded "sewing machine" noise.

Its very simple, If you change ANY of the following:
valve sizes, valve job, head milling, thinner/thicker head gaskets, decked block, cam with an altered base circle, etc... YOU MUST CHECK FOR PROPER PUSHROD LENGTH.

I have helped countless numbers of individuals with this process over the phone, via email, and PM's. I've posted the process on at least 3 occasions.

Here it is again in a nutshell:

1. Using the EO/IC method, get the lifter to the base circle of the cam.
2. Using a known length pushrod (7.400" is a good start with stock rockers) run the rocker arm bolt down to zero lash. This is easily done with your fingers "wiggling" the rocker, the point at which the "slack" is just gone is zero lash.
3. Set your torque wrench to 22 lb./ft. Tighten the rocker to full torque and count the number of turns it takes to get there. 1 full turn wtih a stock 8mm X 1.25 bolt is ~.047" preload as measured at the pushrod/rocker interface.
4. I normally shoot for 1 1/4 to 1 3/4 turns with stock type lifters like Comp 850's, LS1, LS7 etc.

For an example, if you use a 7.400" pushrod and come up with 3/4 of a turn, you will need at least .025" longer pushrod to get into range. If you end up with 2 1/4 turns, you will need one .025" shorter...

I might not know everything but I will tell you that this method has worked for me year after year cam swap after cam swap. We average 3 cam swaps a week here so you can do the math.

If you are not familiar with the EO/IC method for determining valve events in a 4 stroke engine, its very simple:
For a given cylinder as the Exhaust valve is Opening, the intake lifter will be on the base circle of the cam and lash/preload should be checked for that intake valve.
For a given cylinder as the Intake valve is Closing, the exhaust lifter will be on the base circle of the cam and lash/preload should be checked for that exhaust valve.

THIS METHOD ALWAYS WORKS!!!

I hope this helps someone. I have explained it so many times I think I do it in my sleep!!!

Shane_____________________________________________ _____ __________________________________________________ _

ZeeOSix

So according to the chart I attached in an earlier post, those lifters (12576400, 2007-2010 LS7 lifter) would need a pre-load of 1.58 mm = 0.062". That's ~1.33 turns of the rocker bolt from zero lash to 22 ft-lbs.

LilJayV10

iTrader: (39)

This is headed towards epicness.

LilJayV10

iTrader: (39)

Also an accurate way to check PTV clearance.

mannyman84

iTrader: (2)

What I'm saying is that I turned them by hand till I had zero lash. Turned the torque wrench to 22lbs and turned and it stopped about 1 1/4 turn. Once I had all torqued to 22 I turned it by hand and made sure the srpings weren't going to close all the way where to I would bend a rod. Springs didn't close all the way and still had some room till they did and started to go back up. Lifter plung didn't seem to sink a lot either.

z99ls1

iTrader: (12)

1. What did you turn by hand to get zero lash?

2. What are you talking about your springs closing all the way? And what does your springs closing all the way have to do with bending a push rod???

ZeeOSix

If you were on the base circle of the cam when you did that procedure, then it looks like the correct lifter pre-load, which means those pushrods are the right length.

ZeeOSix

He's saying the springs where not in coil bind at max valve lift. If they were going into coil bind, then you could bend a pushrod and/or break a spring.

z99ls1

iTrader: (12)

Figured that's what he was saying, but the way he worded it confused me lol. Also I don't think that is the proper way to look for coil bind. I think you should mesure your open and closed seat presures, and make sure your putting the right springs in there. Not trying to be a jurk here, I'm just sayin....

mannyman84

iTrader: (2)

Z99ls1, I tight down the rocker bolt till I had zero lash on the push rod. Sorry to confuse u. just had to type it quick. Then tightned the rocker at 22 pounds and turned 1 1/4 turns. I did all the rockers like this and then turned the engine by hand and made sure the springs weren't binding. Like going completely closed. Still had about half inch before they did. Then the spring started to go back up. Seems good to me lol. If this doesn't sound good to anyone I will get a pushrod checker and really check the exact length.

z99ls1

iTrader: (12)

Well if you getting zero lash and than getting 1&1/4 turns to 22ft lbs you should have the right pushrod! How are you determening your at zero lash?

ZeeOSix

The spring pressures are based on the spring's rate (lbs/inch) and the spring deflections.

The closed pressure is dependent on the spring's installed height, and the open pressure is dependent on the max valve lift (ie, max spring compression).

Coil bind has really nothing to do with the seat pressures, but strickly on the max expected deflection. At the max valve lift, there should be at least 0.060" clearance between the remaining open coils - and this should definitely be checked on the car.

Choosing the right springs is mostly dependent on the max expected valve lift to ensure there is no coil bind, and that the springs are stiff enough to prevent valve float with the cam profile at max expected RPM.