Date: Tue, 11 Feb 1997 10:08:14 -0800
From: Mike West <mwest@CDSNET.NET>
Subject: VTG, Rocker Shims & Swivel Foots

Well, this is the second part I promised.

In the first part, I bad-mouthed the rocker/valve setup.

Now we look at what we can do.

First, in order to get any spin from these valves, you have to shim the
rocker assembly under the mounting posts to the point where the
adjusting screw tip at least crosses the center line of the valve
stem in it's arc of travel.

To turn any object around on it's center axis, you must exert a force
at right angles to the the center. Cutting thru a chord won't do it.
It must travel in an arc about that center.

I can't explain that better without teaching a course in descriptive
geometry. You can see it for yourself if you'd like to round up a set
of light springs and move the rockers/valves thru their motion.

I had to put .125"(3.2mm) under my rocker assy's to get there.

It would have been less but I installed the "Swivel Foot Adjusters"
as a bandaid for the galling problem.

The difference between the standard adjuster screw and a "swivel-foot"
is the size of the swivel foot on the end of the adjuster.

On the standard adjuster screw it is a ball-point which makes a
theoretical one point contact with the valve stem top.

The swivel foot has a ball bearing in the end and then a flat round
foot mounted to it. So it will turn around the axis of the screw and
has about a 15 degree total tilt movement.

The bearing surface in contact with the valve stem is just about the
same diameter as the valve stem itself.
It also has an oil path built in to get oil to the foot surface.

So while the standard ball end adjuster bears down on one point and
grabs, the swivel-foot bears down on a large flat foot that perfectly
aligns with the valve stem top.

One of the questions was does the swivel-foot prevent rotation of the
valve. No it doesn't,, the force still is there thru the center line
of the foot.

If it were a roller ball or roller it "would" prevent this rotation.

The only way to prevent the rotation of the valve stem is to not have
the adjuster screw pass thru the center line of the valve stem.

So we adjust for all the tolerances and have to shim under the feet of
the rocker assy posts.       Here's the scoop:

Even with the "swivel-foot", you need a couple of new standard
adjuster screws. You can't find the center of the adjuster with the
big foot of the swivel.

I will assume the 4 valve stems are all the same height, if they aren't,
then you have to compensate and sort of "average" your adjustment for the
differences.

Since you can only shim in two spots under the rocker assy those 2
points are for all four points of the rockers.

By the way, you are doing this after you've lapped the valves and
before you put the valve springs on.

For a standard adjuster screw, you set it in the rocker with an equal
amount of thread sticking out both sides of the rocker arm, then lock
it with the lock nut finger tight.

This is to give you adjusting room as the valve wears in or the adjuster
screw wears down.

With the swivel-foot, install the same way and adjust the same way
for an equal amount of thread on both sides of the rocker arm.

Once you have this set on the swivel-foot, you want to take a measurement of
the distance from the rocker arm to the bottom of the foot and then replace
the two end swivel-feet on the rocker assembly with standard adjuster screws
set to the same height.
Mine was about .40 inch(10mm).

Now you have to set up the valve stem itself, the two end ones.

You determine what the full height is, valve fully seated.
Put the spring cap on and the cap retainer clips around the valve stem.

Measure under the spring cap there, for full height where the spring
would be.

Your stock cam has a lift of .320 inches at the valve stem so cut a
piece of 1" PVC pipe, which is about the same diameter as the spring,
to the spring height you measured, less half of the .320".

What you are trying to achieve, is a spacer to take the place of the
spring that will set the valve stem at half it's travel.

In my case that was 1.485" - .160" = 1.325", the length of the spacer.

Apologies to the Metric world, nobody said life was fair.

OK now we put the spacer where the spring goes and the cap and retainer
clips on it.
 Actually, I had to split the spacer because it wasn't short enough to
put the cap on with it in there. So I put the cap and retainers on
and then slid the spacer in under it.

Now we have one end set up with the valve at half travel.
That's all you need right now.

Get the Rocker assy and set it in place and screw it down finger tight.

The adjuster screws are already set.

Holding the valve on the spacer at it's half travel position, lift the
rocker arm over it and sharply rap it on the valve stem.

It will leave a mark on the shiny valve stem top. If it doesn't, use
a pencil to black the end of the adjuster and do it again.

What it looks like is a round dull spot on the shiny surface of the
valve top, about .03" (.7mm) in diameter.

Using any method you choose, measure its relationship to the center-
line of the valve stem. I just lay a short scale across the stem top.

The travel of the adjuster screw across the valve stem that you can
correct is in a direction towards the rocker shaft.

In the direction parallel to the rocker shaft it will always be off-
center but that is the one you can't do anything about.

So looking down the row of valve stems, look where that mark is
relative to the center of the stem.
Odds are it will be too far towards the rocker shaft.

Wipe the spot off the the valve top and put shims under the rocker
assy posts, and mark the stem again by rapping the adjuster on the
stem.

If it's still low, put more shims in, do this till you get it to the
center of the valve stem.

As I said, I ended up with .125"(3mm) under the rocker posts.

Where did I get all the shims?  At my FLAPS. he has a bag full.

I have had to back the rocker assy hold-down studs out to get a full
nut on the stud.

Once you've achieved this on one end, using an equal number of shims
on both ends of the rocker assy, just do a check with your spacer etc.
on the other end.

Now since I put so much height on this assy, I had to check if the
"rocker box" cover would go on. I'm happy to report it goes on and clears
even without the gasket.

I've given some thought to putting swivel-foot adjusters in an existing
engine, in the car.

The best you could do, would be, put all the shims they have in the package
under the rocker assy. That's 2 per post in my pack. .06"

Then adjust the valves as per . . . The .006 or .008 or what.

Now with either the engine running or just turning it over with the
starter, look at those foots and stems down the length of the car and
try to determine if they travel an equal amount across the stem in
their travel.

If it looks pretty good, slap the cover back on.

I know this is long, boring and unclear.

I gave it my best.  :-)


 west