I asked Richard Good about this via email a while back, and he
clarified it for me.
The rocker geometry is affected simply by the height of the rocker
fulcrum, the rocker ratio, and the height of the valve stem tip. The
geometry can be adjusted by shimming the rocker pedestals, if
necessary, but the pushrod length will have no impact.
The only thing pushrod length will impact is the ability to set the
valve clearance properly (ie: too short a pushrod will mean you will
have too much valve clearance, even when the adjusters are at full out;
too long a pushrod will mean you will have too little valve clearance,
even when the adjusters are at full up). As long as you can set the
specified valve clearance, your pushrod length is fine. The adjusters
take care of everything, without affecting rocker geometry.
Tim Holbrook
1971 TR6
--- Greg Dito <dito9561@bellsouth.net> wrote:
> Joe,
>
> My understanding is that if you can get the rocker arm to be
> perpendicular
> to the valve stem halfway through its full travel then rocker
> geometery is
> where it should be. Some of this can be taken up by the adjustment
> screw
> but if the head mill is extreme then shorter pushrods are most likely
> a
> must.
>
> Other ideas include installation of silicon bronze valve guides, and
> cleaning up the sharp edges in the combustion chamber and cutting
> material
> off of the backside of the intake valve for improved flow per
> Kastner's
> manual. Definitely use tubular pushrods, stock pushrods flex too
> much. And
> I'd be kinda leery about using unmatched lifters with the existing
> cam.
> Once the cam lobe and lifter face seat you do not want to mix them.
> While
> lifters can be refaced for $60 or so I would spring for the another
> $60 and
> purchase new hardened lifters. Inexpensive insurance IMHO.
>
> Lightweight valvetrain components reduce mass and allow higher revs.
> However, unless you plan to spend lots of time in the higher rev
> range there
> are probably better ways to spend money for more power and grins.
>
> Greg Dito
> CD6250L
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