Guys I'm getting ready to put my new heads on soon. I have done the whole head and cam swap myself in my garage and it was the first time in my life attempting anything like this. Everything has gone perfect so far, but the thing that scares me is getting the valve train back in tact. What are the most important things to look at when reassembling it? I installed new lifters and pushrods, and I'm getting trunion upgrade on my stock rockers. I made sure I got the measuring pushrod to measure for new ones. My new heads already came assembled with springs, valves, etc. Thanks for any advice.

 

Prior to measuring you should check the rocker geometry, however here is how to measure. Rocker geometry check will vary depending on what rockers are being used.

This is how to measure for pushrods assuming you have the Comp Cams adjustable pushrod, which at its shortest length is 6.800".

Each turn of the adjustable pushrod is 0.050". When fully closed, it is 6.800". This is pushrod "gauge length" so you can't measure it directly as the pushrod length is actually based on the length between the ball ends where the ball end measures 0.140" in diameter. Assuming you are using stock rockers or a non-adjustable rocker.

1. Open the adjustable pushrod to the same length as your stock pushrods
2. Close it down two turns
3. Put your rocker rail on the head
4. Make sure you cylinder (typically #1) is at top dead center on the firing stroke so both valves would be closed
5. Put the pushrod in place on the intake valve and make sure it is in the lifter cup
6. Install the rocker and snug down the bolt (don't need to torque, just make sure it is snug)
7. Lift rocker tip up and down, if it "ticks" the pushrod is too short. If you can't easily move the rocker the pushrod is too long.
8. You can try and adjust the pushrod in place but my fingers are too fat so I end up pulling the rocker and adjusting the pushrod length. Go either shorter or longer 1/2 turn and try again.
9. You are trying to get to the point where the lifter doesn't "tick tick" with the pushrod in place nor is the rocker snug. When you get the pushrod length such that you just barely get rid of the "tick tick", you have found "zero lash".
10. When you have found zero lash, carefully remove the rocker and pushrod without rotating the pushrod.
11. Tighten the pushrod until it is fully closed counting the turns as you go.

To figure out your pushrod length you do the following. Let’s assume it took 10-1/2 turns to close the pushrod down to its shortest length after you reached zero lash. Each turn is 0.050".

Your length is then: 6.800" (fully closed length) + 10.5 X 0.050" (number of turns times the length change per turn) = pushrod length minus preload. So for this case:

6.800 +10.5 X 0.050 = 7.325"

This is the length you measured to zero lash without any lifter preload. Now let’s say you want to have 0.075" lifter preload, you add that to the measured number and you end up with 7.400" pushrods.

Now repeat for the exhaust valve to verify the length. If you have something like Yella Terra's, it is the same procedure but you must snug down the rocker pair rather than the single rocker.

Pushrod Installation

I like to submerged the pushrods in oil prior to installing so they are pre-filled. When I install them I put a finger over one end so they don't drain. I also use Redline Assembly Lube and put some on the top of the pushrod prior to installing the rockers and some on the top of the valve stem. This aids lubrication as it can take several minutes for oil to reach the valve train, especially with new lifters.

If you are using stock rockers, here is the installation procedure.

 

Great Info, copied to file. Thanks.

 

Another thing is drop each pushrod in the hole one at a time,,,and then with a flashlight visually inspect the rod and make sure it is sitting in the middle of the lifter cup, they can get sideways and if you dont check and tighten the rocker you could do some damage, just a simple step to take and be safe.

 

I have never dipped a pushrod in oil, but I would recommend putting assembly lube or high pressure grease on each end of the pushrod and where the rocker contacts the valve tip.

 

Bobs gives outstanding advice and know how knowledge. But here is what I would do: You have a stock length pushrod now I assume, use that to check your wipe pattern and preload 1st, and start from there. That will determine what you have and is given with that length, then you go up or down .025 from there to give you best/optimum results.

 

This really helps. Im getting ready to put my heads on also and bought a pr length checker. This really helps, but what I don't understand is the preload. Im running the stock rockers. once I figure out the pr length how do I determine what my preload will be? I figured once I get the length, then that would be it. What is preload? the tightening down on the rocker? thanks for the help.

 

Lifter preload is the initial pressure applied to the lifter. Unless otherwise noted, most common preload is .030", roughly 1/2 turn after zero lash.

 

Ok gotcha..thanks.

 

The quoted information is not for LS motors. The information above is for older small block Chevies. The LS motors have two differences. 1. The factory rocker arms are not adjustable. So, there is no adjustment, you merely torque them to specs. Here is a handly online resource for LS torque specs: http://www.ls1howto.com/index.php?category=1 2. The lifter preload for an LS motor is typically between .075" -.100".

 

Thanks for that correction

 

So add .075-1.00 for preload. Gotcha thanks.