[DeTomaso] Tech Help needed - NPC - Sizing pushrods for stud mount roller rockers-sbf

[Ken Green]

I had assumed that the goal is to keep the roller as close to the center of the valve stem as possible, but this would mean that the roller starts on the inside, moves past center at half lift, and then returns back to where it started.
 
It is probably a lot bigger deal with high lift cams because the rocker rotates through a greater arc.
 
Ken

--- On Fri, 10/15/10, Cullen McCann <clarkwgriswold2nd at gmail.com> wrote:


From: Cullen McCann <clarkwgriswold2nd at gmail.com>
Subject: [DeTomaso] Tech Help needed - NPC - Sizing pushrods for stud mount roller rockers-sbf
To: detomaso at realbig.com
Date: Friday, October 15, 2010, 9:28 AM


Hello all, ( and maybe Dan if you are still online or listening)



On another project I am setting up valve train on a carbureted 302 with a
flat tappet hydraulic cam, a set of trickflow twisted wedge heads
(2.02/160.'s), with a set of erson cast aluminum roller rockers, stud mount.
I have an adjustable pushrod and I'm trying to determine my required push
rod length. I have determined this before on pedestal mount rockers.its
pretty easy.tighten down the rocker to the pedestal, adjust the pushrod to
the point of zero lash, add length to that number for preload on hydraulics
( cant remember what it was - .030 -.050?) and that is that.



On the stud mount rockers basically all the support I get online is that
correct geometry as the roller tip of the rocker passes over the head of the
valve stem, it should start at ABOUT the first 3rd point, and as the valve
opens it should pass over the center of the valve stem and across to the
last 3rd point. ( this is hard to do without sketching something.) but even
with that geometry governing, the length of the pushrod still seems to be in
a range of +/- ..LOTS, like .250 either way, and I know its more precise
than that. The taller the pushrod the farther towards the center of the
valve stem the rocker tip sits.but it still seems to .VAGUE. What am I
missing?



Thanks for your help!



Cullen



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