vettenuts

iTrader: (4)

You need to buy an adjustable pushrod, its about $20. That way you can take a direct measurement of your setup once the heads are installed and the cam is in place. First check wipe, once you have that nailed then measure for pushrod length.

Pray

iTrader: (7)

Buy or make an adjustable push rod. Summit has them. Just make sure they go from around 7.25"-7.75". Or just make one like I did. I cut an old push rod to my needs and threaded it. But it gets really difficult with hardend pushrods. You are not that far from me. I am in Sanford by Bragg. You could bring your car by my house or borrow mine if you want. PM me if you want my number.

Kurtomac

iTrader: (5)

so how do you know when you have the correct length pushrod/need longer/need shorter?

vettenuts

iTrader: (4)

This is 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.

Kurtomac

iTrader: (5)

good read...should it ever be different on the exhaust? and since the lifters pump up and bleed off when does this need to be done?

vettenuts

iTrader: (4)

Properly prepared heads should be the same, exhaust and intake.

First make sure the lifter is against the cam by pushing it down with the pushrod.

When taking the measurements, even with the lifters in place, the key is to be gentile and do it by feel. You can feel the pushrod contact the lifter, so don't push on it and get a bad reading such that you are depressing the plinger within the lifter. This is another reason to do the exhaust, it ensures some consistency in your measurement technique. If you find a big difference, likely it is with the measurement.

Kurtomac

iTrader: (5)

ok so let me ask this what are the negative effects of a pushrod being too long or too short?...and whats an acceptable tolerance?

vettenuts

iTrader: (4)

Way too long, valves hang open. Way too short, valves don't open all the way and engine is noisy. Stock lifters are pretty forgiving, I have seen people run them from 0.075 to 0.125 preload with the deeper preload being quieter.

Kurtomac

iTrader: (5)

makes no sense why yella terra wouldnt just build the .050 shim in since pretty much everybody requires that much
ok so what the sold me gerally should work at least long enough for me to get an adjustable and check...yella terra ultralites havent opened the box yet...but i hear they come with shims...and TFS 7.500's...heads being milled .020 and using MLS gaskets

The Alchemist

iTrader: (19)

Is it safe to just measure one swipe pattern and pushrod? I mean if we were building a high end road racing endurance motor, we'd be measuring and setting up each one individually, but I'm guessing that there is some built in tolerances that make it ok to just check one. Or am I totally off base. I can't see you ordering 16 different pushrods and shimming the 16 rocker arms differently.

vettenuts

iTrader: (4)

You can't really shim the rockers individually anyhow. I check both the intake and exhaust. This provides a good cross-check to make sure I didn't screw up and also if there is a slight difference you can compromise if necessary. On the rest of the valves I do what I call a tap test, I rub a little grease on the rocker tip and then after snugging it down just tap the valve stem. This will provide a line which is the starting position for the wipe across the valve stem during the opening and closing. You should see these lines are consistent and at the same position as the inner edge of the wipe pattern you checked. But that's just me. I also measure both an intake and exhaust pushrod length as well, again a good cross-check.