[Fot] Harden Valve Seats

[WEmery7451 at aol.com]

Dear FOT,

Whenever my machinist has set up a TR-3/4 engine head for me, he
automatically puts in harden valve seats for both the intake and exhaust valves
.  I gave
one of my engine heads to Dan Styduhar, who has been helping me with the TR-3.
His machinist highly recommends not to put the harden valve seats in for the
intake valve.  A lot of material is ground out the cast iron head to install
the valve seats, and there is not a lot of material between the intake and
exhaust valves to begin with.

My initial guesses would be:

-There are two different materials involved -- cast iron and steel.  Maybe
the steel valve seats would not count as material being replaced, and that the
cast iron could crack under the seats.

-If there is not a great deal of exhaust gasses blowing past the closed
intake valves, the intake valves would not need the harden seats -- keeping in 
mind
that there is a tremendous pressure surge during the combustion stroke.

Does anyone have any thought on this subject?

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