A Must If You Are Doing
Complete Valve Jobs, Touching Up
Seats Or Just Checking Another Shops Work
Concentricity - Quickly And Accurately Measure Valve Seat Runout
Seat Depth - Valve Seat Depth Consistency Between Cylinders Is An Absolute
Must To Compression Ratio And Piston To Valve Clearance. Allows
You To Maintain Seat Depth To Deck Clearance Within .001 Inch
Seat Width - Consistent And Accurate Seat Width Is A Must For Horsepower
And Endurance. Allows You To Blue And Scribe Each Seat Width For
A Grinding Reference
Stem Height - A Lot Of People Overlook Stem Height With Adjustable
Rockers. This Is A Real Mistake As Mismatched Stem Height Will Cause Havoc
With Valve Train Geometry
Available In All Popular Pilot Diameters - .375", .385", .437
(Other Sizes Not A Problem)
Comes Complete With Dial Indicator, Fitted Box, Instructions And Helpful
Tips For Competitive Valve Jobs
Stem Height: Assemble
(Don’t over-tighten collet as this will damage the indicator.)
To measure stem height variation, simply move
tool from one valve to the next and record the difference in
indicator readings. Stem height is
critical on non-adjustable rockers and should be recorded BEFORE
a valve job and duplicated after a
valve job by tip grinding.
Scribing Valve Seats: Assemble
tool with sliding stop in collet and with the scribe trailing in the
direction of rotation.
Seat. - Adjust scribe to desired
diameter and scribe bottom and
top of seat. Grind as little as possible to clean up seat to desired
NOTE: Sinking valves
and sinking elapsed time go hand in hand.
do not exceed 1/32” valve overhang, as more than this interrupts heat
dissipation and disturbs maximum air flow. Throat
bottom angle with 60-degree stone to establish final seat width.
Valve Seat Concentricity:
Assemble tool. Place
fixture over the pilot. (It
is best to check concentricity BEFORE
removing pilot after valve job.)
scribe to track on center of the seat.
fixture, being very careful not to apply side pressure, as this will
cause false readings.
will record high and low sides of the seat.
grinding to correct run-out, apply very light pressure toward the high
indicator run-out should not exceed .003”.
An eccentric (off center)
valve will seat, so it can’t be detected with a leakdown meter.
But, in doing so, the valve head has to slide sideways to seat.
This happens every time the valve opens and closes.
This sliding action bends (flexes) the stem which in turn applies
pressure to the guide which causes rapid wear.
This sliding movement also reduces the time the valve is on the
seat which reduces heat dissipation and promotes burned valves and
pre-ignition. All of this is
bad, but the worst part is the valve cannot breathe properly when it is
sliding sideways. Incidentally,
loose guides will also do all of the above.
for Good Valve Jobs
Below are a few suggestions which P.M.S. has tried and feel are correct.
It is true that there is horsepower to be gained through radius
seats, etc., but if you don’t have a good flow bench, dyno, and a hell
of a lot of time, you will be ahead of most by sticking to sound basics
– which aren’t that shabby anyway!
Face 45 degrees x .100” wide
Undercut 30 degrees to obtain proper face width (if rules permit)
Face 45 degrees x .080 wide
Undercut 30 degrees to obtain face width
Radius margin corners
45 degrees x .080” wide
2. Top cut 30 degrees
3. Throat 60 degrees
1. Seat 45 degrees x
2. Top 30 degrees
3. Throat 60 degrees
for Measuring Seat Depth
Attach indicator to
Concentricity Tool sleeve.
Slide over grinding
Set rounded point
against valve seat and tighten point with Allen wrench.
Set dial indicator on
deck surface (try and keep indicator parallel to pilot).
Swing in an arc to
obtain lowest dial indicator reading.
Set dial to “0”.
Grind seat to desired
Take a reading on
indicator and reset to “0”.
Grind all seats to
Check for Leakage
Fill port with water
Blow around valve and
seat with an air gun – 80 to 100 psi.
bubbles appear in port, take it apart and fix it