<VV> Clarks Roller Rockers

Mon Sep 2 18:48:02 EDT 2013

Bob, most people need to know how to get the correct length push rods to
use with the roller rockers. Or at least see if the std ones are a good
length. All of my std ones were too short, due to a reground cam and height
adjustments at the valves due to grinding/lapping in. I also replaced all
the valves, which means the height at the stem end can be a little bit
lower due to a fatter valve face than from the previous valve work. There
is no such thing as "new" anymore, we are adjusting everything to get to
some semblance of normal for the valve geometry.

The attached valve train geometry link will be a great help. It shows where
on the valve stem you want the roller to work, the middle third.

Rather than spend the money and buy the solid lifter kit, which required
calculations, I simply took a push rod of a known length, one of my used
ones that was to new spec, and put that in place, then added the roller
rocker (also requires calculations) . With the engine at TDC for that
cylinder to keep the lobes out of the way, I screwed down the rocker nut
until the roller of the rocker just touches the valve stem. I insert a
piece of paper in the gap and pull on it. When there is drag, I stop.

Then I check to see where on the valve stem the roller is touching. If the
roller is not at a point just below the center of the valve stem (It needs
to run from 1/6 below center to 1/6 above center or the center 1/3 of the
valve stem), you need to make adjustments. All of my push rods were too
short, so I slowly backed out the rocker nut until when I rolled the rocker
over to touch the valve face with the rocker pulled tight against the
adjusting nut, the roller was at the correct spot on the valve stem face,
then I tipped the rocker back to take up any slack being careful not to
compress the lifter (gently took out the slack but was still able to turn
the pushrod, you do this with no push rod tubes in place), and measured
the distance between the rocker roller and valve stem face.

For example purposes, lets say I measured .075 gap.

Remember that the rocker works in a ratio. Clarks use a 1.58 to 1 ratio
like stock rockers, which means for every .001 of movement at the push rod
end of the rocker, the roller end moves .00158 so you have to divide by
that to get the correct length at the push rod end.

Example, If you measured .075 clearance at the roller rocker to valve stem
face, it looks like this:

1.58        .075      Invert and multiply so:
------  X   ------      1.58 X = .075 so 1X is .075 divided by 1.58 or
 .047468 or .047.
1                X

This means you need to buy a push rod approximately .050 longer than a
standard push rod.

Clark's push rods come in a bunch of different lengths, and I discovered
during my measuring, that .020 to .030 one way or another does not make
much difference in the placement on the valve stem. And, so I ordered
Clarks as close to the required length I needed and installed them, then
checked every one at zero lash to ensure I hadn't "goofed" somewhere. All
12 operated on the valve stem face in the middle as needed.

If none of this makes sense. Let me know! My engine was adjusted cold and
dry with the new push rods 2 years and 4,000 miles ago, and after a pre-oil
and break-in period, the rockers have operated perfectly. There has been no
need to adjust or readjust the valves, I set them to 1/4 turn in from zero
lash. The engine now has a unique additional singer sewing machine sound to
it.

If you want to know what other mods I did to the engine, I would be happy
to share, if you are looking for ideas.

Regards

Mark Durham
62 vair coupe
red/red
64 110 modified.

On Mon, Sep 2, 2013 at 1:04 PM, Mark Durham <62vair at gmail.com> wrote:

> Hi Bob, I installed a set 2 years ago on my engine. I also installed
> the longer shafts and a set of Clarks aluminum valve covers for
> clearance.
>
> Pointers. Hmmm. I bought Clarks custom push rods, measured specifically
> for each valve. I did not use the much publicized kit to measure for
> push rod length.
>
> Send me a note with details of your project and where you are and I can
> give you some pointers Based on your data.
>
> Mark Durham
> 62 Coupe 4 speed red/red
> Modified 64 110
>
> Sent from my Windows Phone
> From: Bob Gilbert
> Sent: 9/2/2013 9:38
> To: virtualvairs at corvair.org
> Subject: <VV> Clarks Roller Rockers
> Hi,
>
> Has anybody out there installed a set of Clarks roller rockers?
>
> If so, any hints or tips would be appreciated.
>
> Regards,
>
> Bob
>
>
>
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-- 
Mark Durham
Hauser, Idaho
62 Monza coupe Red/Red 4 speed
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