12V Head Thickness?

DieselAddict1on

DieselAddict1on

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Anyone know the standard thickness of a 12V head? I bought one today that has been decked, and I want to know If I need a thicker gasket. The PO did not know how much was taken off in the process.

Thanks
 
You only need a thicker gasket to prevent valve-piston contact. You can measure the valve depth and compare to what it should be and it'll dictate if you need a thicker gasket. If you search some of Zach Hamiliton's posts, he has stated what the valve depths should be. Weston could probably help you out as well.
 
You'd need a thicker gasket to avoid piston to valve contact ONLY if a valve job was NOT performed after the head was machined which is the proper way to machine a head. My Cummins Shop Manual specifies valve depth anywhere from 0.039"-0.060". To further quote a short section:

Record the depth of each valved as "A."

It then goes on to say that if the valve depth does not meet specs, the seat must be replaced. If the valves meet the initial depth criteria, grind the seats to remove all scores, scratches and burns. Seat angle for the intake valves is 30degs. and for exhaust is 45degs.

Since the seats have been ground or replaced, it is necessary to re-measure valve depth and to calculate grinding depth. Install the valves in their respective bores and measure the depth. Record the depth of each valve as "B." Make sure the seats are clean before measuring.

Calculate grinding depth (GD) as follows:
GD = B - A.

The GD limit is 0.010". Service valve seats are available for over the limit seats.

Confirm that the valve depth after grind (B) is still within the original spec of 0.039"-0.060".
Click to expand...

It continues after that, describing the procedure for centering the valves and measuring the valves for seat width and centering but, that may be more info than you're after.
 
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