Valvetrain gurus ? about geometry
09-12-2005, 02:57 PM
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Valvetrain gurus ? about geometry Refering to JRP's cam guide 5/28/05 Holly.com post
Is this necassary to do when changing cam's and springs? I would imagine so, though i haven't heard of anybody mentioning the use of an adj pushrod during their installation of a cam.
Is this something you need to do before buying pushrods? To ensure you buy the right length rods? If I go out and buy 7.4" rods stock length whatever it is how will i know they are what i need. Or does this whole procedure only apply to more radical changes. ie Milled Heads, Huge cams with massive lift, etc?
Sorry just trying to learn........
Is this necassary to do when changing cam's and springs? I would imagine so, though i haven't heard of anybody mentioning the use of an adj pushrod during their installation of a cam.
Is this something you need to do before buying pushrods? To ensure you buy the right length rods? If I go out and buy 7.4" rods stock length whatever it is how will i know they are what i need. Or does this whole procedure only apply to more radical changes. ie Milled Heads, Huge cams with massive lift, etc?
Sorry just trying to learn........
09-12-2005, 03:12 PM
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read a few hot rod magazines...
If you change rocker arm sizes - 1.7 to 1.8 etc. you will change the geomatry which could require different length pushrods... changing valve length will also change geometry....
Cam size should not impact the geometry.... ditto with lifters that are stock sized....
If you change rocker arm sizes - 1.7 to 1.8 etc. you will change the geomatry which could require different length pushrods... changing valve length will also change geometry....
Cam size should not impact the geometry.... ditto with lifters that are stock sized....
09-12-2005, 03:21 PM
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But milling the heads and changing the gasket from stock size changes geometry too. And an aftermarket cam can have a smaller base diameter than stock, which would require different length pushrods.
Use an adjustable pushrod and do the swipe test so you KNOW instead of trying to guess over the net. I can tell you by experience if you have too long a pushrod the car won't get compression and the valves will hang open. Too short a pushrod and the car isn't getting it's full potential because the valves won't open all the way.
Use an adjustable pushrod and do the swipe test so you KNOW instead of trying to guess over the net. I can tell you by experience if you have too long a pushrod the car won't get compression and the valves will hang open. Too short a pushrod and the car isn't getting it's full potential because the valves won't open all the way.
Last edited by Viper; 09-12-2005 at 03:29 PM.
09-12-2005, 04:28 PM
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Originally Posted by Viper
But milling the heads and changing the gasket from stock size changes geometry too. And an aftermarket cam can have a smaller base diameter than stock, which would require different length pushrods.
Use an adjustable pushrod and do the swipe test so you KNOW instead of trying to guess over the net. I can tell you by experience if you have too long a pushrod the car won't get compression and the valves will hang open. Too short a pushrod and the car isn't getting it's full potential because the valves won't open all the way.
Use an adjustable pushrod and do the swipe test so you KNOW instead of trying to guess over the net. I can tell you by experience if you have too long a pushrod the car won't get compression and the valves will hang open. Too short a pushrod and the car isn't getting it's full potential because the valves won't open all the way.