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Discussion Starter #1
Hi experts,
I need help determining the correct pushrod length for my 406, aluminum head, Comp XR300HR cam, and Comp fuller roller rockers. I have the blue Proform checking tool and the Comp adjustable pushrod length checker, but it still insnt clear to me.

I understand that once in the ballpark on length, you have to rotate the engine and look at the wear pattern, but not that far yet.

The Comp site says that the correct pushrod geometry is when the roller is on the inside (intake) edge of the valve stem, in the center of the stem at mid-lift, and on the outer edge (header side) at max lift, this seems backward to me when I look at things.

I would appreciate any and all help with this subject, and you guys are the ones to help me.

Thanks in advance as always,
RJ:sad:
 

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Yeah, sounds right. Give it a shot. You've got the right tools. These are stud mounted rockers, right?
Disclaimer: I'm not an expert. Just a guy who learns the hard way.
 

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I don't use a 'Pushrod' checker.
I like to use the complete Valve Train intended for that engine to arrive at the 'correct' length.

I coat the top of the valve stem with a marking die (or you can use a black marker), install one lifter, one rocker and an adjustable pushrod (set to the 'Zero-Lash' length) and pre-load the lifter if required.
Turning the engine through @ one revolution will mark the top of the valve stem to show contact pattern.
The mark being to 'high' (towards the intake manifold) on stem usually indicates the need for more length - the mark being 'low' (towards the exhaust manifold) on the stem indicates you length is to long for your set-up.
Adjust the checker and recheck until the pattern is closely centered in stem and the contact area mark is the smallest/narrowest (width) you can achieve.

This method incorporates all the variables in stack heights in the system and gives you a very accurate length reading.
Do intakes and exhaust on several valves on both sides until you get a good set of base numbers to order your pushrods from.
I do every valve on some engines ;)

Been doing this for years to compensate for block-head stack, lifter type/size, rocker ratio, and valve length ...
 

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John, what's the difference between an adjustable pushrod and a checker?
 

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John, what's the difference between an adjustable pushrod and a checker?
The 'Checker' sits on the rocker stud and gives you a contact plane to establish a base pushrod length - it does not move through a valve action cycle to allow it to show stem contact.

An 'Adjustable Pushrod' is just that - a pushrod you can make longer/shorter as required to allow you to check it's interaction with the lifter/rocker and valve stem to see what effect the length is having on geometry.

There a numerous variations in a valve trains' geometry - lifter bore trueness, rocker measurement(s), rocker stud location variations, valve guide variations and ect. - that effect the actual pushrod angle and length and it's interaction with the rocker arm, which effects the contact on the valve stem.
Getting the correct pushrod length is a very easy compensation to some of these variations.
 

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Thank you John. Do you hold classes? Can I attend?
 

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Discussion Starter #7
When you use the blue pushrod checker, then you don't have a rocker arm on, so the pushrod can move back and forth in the guide slot, so how do you get much of an accurate pushrod length initially? I mean I guess you would be within an eighth or so, maybe less.
RJ
 

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When you use the blue pushrod checker, then you don't have a rocker arm on, so the pushrod can move back and forth in the guide slot, so how do you get much of an accurate pushrod length initially? I mean I guess you would be within an eighth or so, maybe less.
RJ
RJ check out the post i left under proform pushrod checker it explains everything you need to know about pushrod lengths.
 

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Discussion Starter #10
Checked it out Mike. looks easy enough. I don't have a solid lifter at the moment. I DO have the lightweight checking springs. Can't I use them instead of the solid lifter? They shouldn't cause the hydraulic lifter to collapse I wouldn't think.
RJ
 
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