Date: Thu, 9 Jan 1997 01:07:14 -0800
From: Mike West <mwest@cdsnet.net>
Subject: Valve Train Geometry, Theory meets Metal

The "Old womans" Rocker Arm Assemblies finally meet the Rasty Old
Rebuilt Heads.

I shouldn't have looked.

OK, the valves are all in and the stems are within a 32nd of an inch
of being the same height. Supposed to all be the same.

You want them closer, you grind them. May still take it off the stem.

I really need new seats, these are just getting too low in the chamber.

So then I set the rocker assemblies in place.

Looking down from the intake side like they were on the engine, the
adjusting screw center should be in the center of the valve stem.

Every one of the rockers is riding on one side or the other in the
area of 3/4mm to 1mm. (.03-.04").

What's going to happen if I don't straighten this out is they will
be cocked and wear cocked and the more they wear the worse the cock is.

If that isn't bad enough, what's happening on the valve end?

It is not lifting flat and there's leakage. Which accelerates the
burning of valves too.

So I have to straighten this out.

In a couple cases, it's just a shim job, against the wavy washer side.

In two other cases I have to take that 30 thou. off the rocker assy
post, the one the stud goes thru that bolts them in place.

It would be better to take it off the rocker arm itself but those things are
harder than Japanese Arithmatic.

The posts at least can be cut.

Not having a mill tho, I'm going to have to file and stone them.

Then there's the other direction. Looking fore and aft down the row
of stems.

In that direction they should be some yet undetermined height above the
center and will travel a path across the center to an equal distance below
the center.

Once again, just eye-balling it so far, it looks like I will have to
shim one end of at least one rocker assy to get those parameters in
line.

I've got to round up some light springs tho so I can put them thru the
motion they will travel up and down.

You guys with me so far? If you get lost, I'll meet you in the bar :-)

The light springs are to take the place of the real ones so I can move
them by hand instead of standing on them.

Anyway, once I get them eye-ball close, I'm going to  blue the
ends of the stems and move them thru the arc.

The "arc I'm talking about is the line of travel that the rocker arm
goes thru while lifting the valve to it's full height as determined
by the lobes on the cam shaft.

 The total lift is something like .32" on a stock cam and rocker.
 Can't find my numbers right now.

Then I pull the assy and look at the line worn thru the blueing by the
adjuster screw.

Measure and correct each rocker again.

I'm disgusted at how far these are out.

Well, I'll keep you posted of any further developments.

Since this sort of thing only happens to me, I'm sure yours are all
OK. You would have mentioned it otherwise, right?  :-)

west