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

Instructions

Measuring Stem Height:  Assemble gauge. (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.

Blue Seat. - Adjust scribe to desired diameter and scribe bottom and top of seat. Grind as little as possible to clean up seat to desired width. NOTE:  Sinking valves and sinking elapsed time go hand in hand.

• After grinding seat, top with 30-degree stone (for 45-degree seat).

Also, 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.)

Adjust scribe to track on center of the seat.

“Zero” indicator.

Rotate fixture, being very careful not to apply side pressure, as this will cause false readings.

Indicator will record high and low sides of the seat.

When grinding to correct run-out, apply very light pressure toward the high side reading.

Total indicator run-out should not exceed .003”.

Facts About Concentricity

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.  

Suggestions 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!

Instructions for Measuring Seat Depth

1. Attach indicator to Concentricity Tool sleeve.

2. Slide over grinding pilot.

3. Set rounded point against valve seat and tighten point with Allen wrench.

4. Set dial indicator on deck surface (try and keep indicator parallel to pilot).

5. Swing in an arc to obtain lowest dial indicator reading.

6. Set dial to “0”.

7. Grind seat to desired depth.

8. Take a reading on indicator and reset to “0”.

9. Grind all seats to this depth.

Quick Check for Leakage 

1. Assemble head

2. Fill port with water

3. Blow around valve and seat with an air gun – 80 to 100 psi.  

If bubbles appear in port, take it apart and fix it 

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