Durango Deuce Engine Parts VI
Close up of a valve contact patch. This seating band is extremely important. You must have full contact all the way around the valve. The seat on the right showed no contact (the purple area on the upper right corner).

If the seating surfaces are not perfect, the valve will leak under the extreme combustion pressures (over 1,000 psi)

Narrowing the seat width will increase the unit load or pounds per square inch seat pressure.

Wider seats last longer. Too wide or too narrow is bad. Seats shouldn't be taken to extremes.

Note:
This page will get updated as soon as I can get a better picture. It was brought to my attention that the margin doesn't look right on the valve shown, so for now use this for illustration only.
Here's an example of chatter. This was found on a brand new head that was supposedly ready to assemble. I always check the seat with machinist dye and regrind both the valves and seats for a perfect seal.
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