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Tim,<br>
<br>
I can pass on the suggestions I found in David Vizard's books.
0.080" or so on the exhaust seat width will better carry away heat.
Heat rejection coating for the valve heads means the intake mixture
is pre-heated to a lesser degree and the exhaust has less heat to
hand off to the guide and valve seat. You could use a heat
rejection coating also on the piston crowns, the combustion chambers
and exhaust ports as long as you're in there.<br>
<br>
Leave a sharpish edge on the outer edge (combustion chamber side) of
the intake valve to give some slight anti-reversion effect, but
round it off on the exhaust valve. Exhaust valve can be more
tulip-shaped but intake ought to have a fairly flat back cut angle
since at high lift the nearly 90 degree turn from the intake
manifold will see flow passing somewhat laterally across the back of
the valve. If you can get the back angle to 20 degrees that ought
to improve flow.<br>
<br>
Had you considered 30 degree seats? Flow at low lift is greater,
like having substantially larger valves, without much power penalty
unless you have a huge amount of lift. The tricky part is
maintaining adequate sealing -- dry lube coating of the seat would
help, as would an extra 10 lbs seat pressure. Vizard also found
that a "conformance groove" cut (explained in his books -- if you've
seen Rimflo valves, they have a groove that is similar) around the
perimeter (on the face) allows the valve head to flex just enough to
seat better. <br>
<br>
Duncan<br>
<br>
<div class="moz-cite-prefix">On 2/16/15 7:00 PM, Tim Murphy via Fot
wrote:<br>
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<p class="MsoNormal">I am having new exhaust valves made with
Manley XH-428 stainless steel, a super stainless. It is good
for exhaust gas temperatures up to 1350 degrees. On tearing
the engine down for a rebuild we found that the exhaust valves
were severely “dished” on the seats, we think from the high
heat. The valves were only contacting the seat in a very
narrow (about 0.020) line at the end of the seat width. We
did have good power but the compression test and especially
the leak down test showed there to be some problem. At WOT we
run between 1200 to 1300 degrees. I have to supply Manley
with the dimensions and angle of the valves I need. It is a
bit difficult to measure accurately the back cut angle and
width I’m not sure if the corners should be sharp, broken of
have a corner radius.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">The workshop Manual shows a seat angle of
45 degrees and a seat width of 0.060 with a head diameter of
1.438 inches (36.51 mm). I don’t know what the margin should
be. I also have to give them the groove type, height, depth
and radius for the keepers.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Any help and/or suggestions for what would
make a better racing valve would be appreciated. Note: Manley
has pre-made “blanks” out of various super stainless already
made up. This makes the cost of the valves realistic. I found
one part number that can be make into a TR4 exhaust valve.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Tim and Ryan Murphy<o:p></o:p></p>
<p class="MsoNormal">1961 TR4 #317 BRG<o:p></o:p></p>
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