Z06 heads and pushrod length decision.
Thread Starter
Staging Lane
Joined: Feb 2014
Posts: 72
Likes: 1
From: Lyons, Colorado
Z06 heads and pushrod length decision. I'm assembling a TSP 383 with Z06 heads and using an adjustable pushrod I've determined that my intake pushrod length is 7.05 @ zero lash and exhaust pushrod length @ zero lash is 7.245. Depending on what preload I use for my LS7 lifters (there appears to be no agreement here about what preload to use with them), I'm going to have to decide on a pushrod length that will work for both intake and exhaust. I've calculated that if I use the longer exhaust valve measurement of 7.245 and add .80 I get 7.325 length. Obviously the intake side will be a little shorter, but should work? Anyone care to chime in with a recommendation?
I'm assembling a TSP 383 with Z06 heads and using an adjustable pushrod I've determined that my intake pushrod length is 7.05 @ zero lash and exhaust pushrod length @ zero lash is 7.245. Depending on what preload I use for my LS7 lifters (there appears to be no agreement here about what preload to use with them), I'm going to have to decide on a pushrod length that will work for both intake and exhaust. I've calculated that if I use the longer exhaust valve measurement of 7.245 and add .80 I get 7.325 length. Obviously the intake side will be a little shorter, but should work? Anyone care to chime in with a recommendation?
Perhaps those seats needed a larger valve put in there to restore the proper height
If true in this scenario.....definitely NOT good
Thread Starter
Staging Lane
Joined: Feb 2014
Posts: 72
Likes: 1
From: Lyons, Colorado
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Staging Lane
Joined: Feb 2014
Posts: 72
Likes: 1
From: Lyons, Colorado
I just did that and then carefully measured turns past zero lash using the adjustable pushrod set at 7.325 and got 1 1/8 on the intake, and 1 3/8 on the exhaust.
Thread Starter
Staging Lane
Joined: Feb 2014
Posts: 72
Likes: 1
From: Lyons, Colorado
I just carefully remeasured my zero lash lengths by turning the engine until the exhaust valve on number 3 closed and then stuck a paper towel in the plug hole and let compression blow it out. I then watched the piston get to the top and measured 7.2335 on the intake side and 7.217 on the exhaust side. If I add .080 to those numbers it would seem that a 7.3 inch pushrod is in order.
What is the lift? If they are the same lobe the lift should only be a couple thousands different. If so the base circles should be almost identical. Leaving the valve seat and valves themselves the only reason for the difference.
The .010" lower intake tip could make for some of the difference between the int and exh lengths.
Check a couple other cylinders as well.
The .010" lower intake tip could make for some of the difference between the int and exh lengths.
Check a couple other cylinders as well.
Thread Starter
Staging Lane
Joined: Feb 2014
Posts: 72
Likes: 1
From: Lyons, Colorado
What is the lift? If they are the same lobe the lift should only be a couple thousands different. If so the base circles should be almost identical. Leaving the valve seat and valves themselves the only reason for the difference.
The .010" lower intake tip could make for some of the difference between the int and exh lengths.
Check a couple other cylinders as well.
The .010" lower intake tip could make for some of the difference between the int and exh lengths.
Check a couple other cylinders as well.
Okay, that with the shorter intake valve should make up for the difference of .016" between the two. More lift means smaller base circle.
Your early numbers were way too far apart but the later numbers make sense.
Your early numbers were way too far apart but the later numbers make sense.
Thread Starter
Staging Lane
Joined: Feb 2014
Posts: 72
Likes: 1
From: Lyons, Colorado
I'm getting the hang of measuring I think, it really helps to be able to measure the pushrod. And after doing it a few dozen times it gets easier.