Honk3X

Asking for a friend

Next week I am going to help my friend do a H/C install on his Z.

In the past I have found preload using this method on ls1/2/3. Ive never done an Ls7 yet. does this process still work?

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!!!


His cam lift is .642/.641

I know that stock is 7.800 and im sure his cam has a smaller base circle than stock. His heads have not been milled, we are using stock headgaskets and Ls7 lifters.

I suggested 7.825 atleast.

What do you guys think??

Tech

Get a pushrod length checker.

Must_Have_Z

Mic drop.

Honk3X

We are on crunch time and my pushrod length checker got bent by a friend

Tech

You can get one next day from Summit. Even their regular shipping would have it on your doorstep (assuming you don't live Alaska, Hawaii or in the middle of nowhere) early next week.

MTBSully

Assuming you have a pushrod length checker, anyone have the correct steps to check and measure pushrod length? Link?

Sorry to Hijack. I have used that method before on my old LT1 camaro a few times with no issues.

Tech

http://www.horsepowerlovers.com/how-...th-for-an-ls1/

LT1s made it easier to spin the pushrod. With LSx, you have to rely on the up/down movement of the rocker tip.

MyLS1Hauls

7.825" will most likely work fine with stock lifters...For your case, you should be able to measure the new cam's base circle and subtract it from the original cam, divide by two, and that will get you the amount of length you need to add to the stock pushrod length to maintain the same preload as stock.

FWIW, I built my own adjustable pushrod from an old LS1 pushrod, a 10-32 screw, and 2 nuts. Took about 15 minutes and about 50 cents worth of materials.