i know when adding the yella terra rockers, you should check the pushrod length needed even though most people don't end up changing them. but my question is, did anyone have to change them? i dynoed a low and have a nasty valvetrain tick and i bought the yella terras already and don't care to take them out, and i don't know how to check otherwise. any input? thanks

Jacob

 

The Yella Terra instructions, in a word, suck. You need to check the wipe pattern first, then make an adjustment to pushrod length. I have found that on the stock heads the shims that are provided were necessary to obtain the correct wipe. Once you do that, your pushrods will be too short. Since the shims are 0.050", the pushrod length will change by approximately 0.082". With an aftermarket cam, using stock lifters and the shims, we measured 7.500" as the required pushrod length.

Bottom line, check the wipe pattern first. Once you correct it, use an adjustable pushrod to determine your pushrod length to obtain the required pushrod preload. It will help your motor rev better as well because if you didn't use the shims I am willing to be the rockers are wiping on the intake side of the valve stem with stock heads and a cam installed.

 

thats what i needed to hear. i have 243 heads, a high lift cam, ls7 lifters, and stock length pushrods. doh!

 

So I have stock rockers, 243 heads milled .015, 7.4 PR's, Torquer 2 cam and LS7 lifters and it ticks and clacks like a sumbitch but, you're saying I need longer PR's? As far as I know I need shorter ones...around 7.350

 

IMO the only true way to know is to measure. Anything else is just a guess.

 

No vettenuts is right by adding the shim (if Needed) you are increasing the lifter to rocker arm length then by milling you subtract your milling amount.

 

With a fixed fulcrum rocker, wipe first then pushrod. Measure, its the only way to determine for sure what length is required. I am in process of getting new AFR heads. My first step will be to remove two springs and install checking springs so I can bench check wipe pattern.

 

Ok, I dont mean to sound like a complete car idiot but how do you use the PR length checker (i got it in the mail today). As far as I know you would:
1. Put checker in place of 1 PR.
2. Hand tighten rocker on said checker (but theyre not touching due to 6.8 length).
3. Twist checker and for every turn its adding .050 to 6.8 default setting
4. Turn until checker touches rocker.
5. Add # of turns to 6.8 and voila there's your PR length.

 

Each turn of the 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 buy 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. Lets 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 lets 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.

 

to me, the rocker looks like it wipes perfectly fine with the two shims. i guess i gotta just have someone do it for me. good luck knightrider

 

Hey vettenutts, where was this when I was measuring my PR's? That should be stickied.

 

I just had the Yella Terra Ultralights installed on my LS1 build. The machine shop measured the pushrod length and it ended up needing just the 7.4 pushrod. But My heads have also been milled, and I have a higher lift cam as well. TEA LS6 Stage II heads milled to 59cc, Vengeance Vindicator cam, and Yella Terra ultralights, LS7 lifters...

 

unrelated, but that sounds like a killer package!

 

Timing is perfect for me, I do this next month. Copied it to a file so I'll have it when I'm ready. It should be a sticky