<VV> Heat Treating Heads

[james rice]

Harry: I remember Jon mentioning heat treating the heads on his GT3 racecar.

Any chance of you getting him to outline the process and heat treat hardness
specifications?  	Did he remove all the valve seats and reweld the holes
first?
	Did the heads ever warp or change critical dimensions or size?
	Do we assume after heat treating he warmed the heads and cooled the valve
seats and pressed in the seats with an interference fit?  To what
temperatures and fit?
	Did the angles on the seats make any difference on valve seat life
expectancy?
	Critical question:  Did he ever loose a valve seat of a heat treated head?
	What did it cost then?
	Who did the heat treatment?

If the process can be documented, is there any commercial applications for a
vender as replacement heads?

Historically Yours,
			James Rice


Hello--

The engine in Jon Brakke's Corvair SCCA race car used to loose compression
in a couple of cylinders after a couple of sessions. We used to religiously
do a leak down test and if the compression was down, we'd pull off the heads
and lap in the valves. Jon's theory was the seats were moving slightly.

He eventually had the heads heat treated. I'm pretty sure the heads use the
aluminum alloy 356 which then is heat treated. After many, many years of
heat cycles, the aluminum losses its hardness.

After the heat treating, we never had a compression problem due to leaking
valves again.

--H