Push rods
Team Owner
Joined: Mar 1999
Posts: 22,025
Likes: 192
From: At the beach in little Rhody
Base circle is a direct measurement (change in base circle is change in pushrod). Valve stem length goes through the rocker ratio, .100" taller valve stem is 0.059" change in pushrod length.
The bigger issue is correcting the rocker geometry before you do anything. The taller valve stem will shift the wipe pattern towards the intake manifold and needs to be corrected prior to checking pushrod lenght. Then measure.
The bigger issue is correcting the rocker geometry before you do anything. The taller valve stem will shift the wipe pattern towards the intake manifold and needs to be corrected prior to checking pushrod lenght. Then measure.
Pro
Joined: Oct 2001
Posts: 668
Likes: 26
From: Wadsworth Ohio
Base circle is a direct measurement (change in base circle is change in pushrod). Valve stem length goes through the rocker ratio, .100" taller valve stem is 0.059" change in pushrod length.
The bigger issue is correcting the rocker geometry before you do anything. The taller valve stem will shift the wipe pattern towards the intake manifold and needs to be corrected prior to checking pushrod lenght. Then measure.
The bigger issue is correcting the rocker geometry before you do anything. The taller valve stem will shift the wipe pattern towards the intake manifold and needs to be corrected prior to checking pushrod lenght. Then measure.
Team Owner
Joined: Mar 1999
Posts: 22,025
Likes: 192
From: At the beach in little Rhody
Not on these cars. The rockers are a fixed base and the only way to alter the wipe pattern is to shim the rockers up or cut the base depending on which way the pattern needs to be shifted.
Team Owner
Joined: Mar 1999
Posts: 22,025
Likes: 192
From: At the beach in little Rhody
Since the valve stems are taller I would think the rocker base needs to be raised. Here is a link to a thread where I shimmed a set of Yella Terra rockers, same principal applies to the stock rockers if that is what you are using. In my case, the valve stems were taller as well as I ended up with a fairly stout shim. If the heads are off the car, you can do this on the bench. Link
Thread Starter
Instructor
Joined: Dec 2008
Posts: 127
Likes: 0
From: Grand Rapids Mi.
push rods
To VetteNut, Where can i find shims for the stock rocker arm setup and given my problems would i need longer or short rods. My heads are on my car,where can i find info on checking my rods. Thanks
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Team Owner
Joined: Mar 1999
Posts: 22,025
Likes: 192
From: At the beach in little Rhody
Shims can be had from Ford. See this link: Link
I am guessing you will need to raise the rocker pivot height due to the longer valve stems. For each 0.010" of shim you will need approximately 0.016" of pushrod length but measure for a final value.
To check the wipe with the heads on the car, best to do with check springs and a dial indicator. Rotating the motor will compress the lifter plunger and you will get skewed readings.
I am guessing you will need to raise the rocker pivot height due to the longer valve stems. For each 0.010" of shim you will need approximately 0.016" of pushrod length but measure for a final value.
To check the wipe with the heads on the car, best to do with check springs and a dial indicator. Rotating the motor will compress the lifter plunger and you will get skewed readings.