[Fot] dimensioned drawing for stock TR4 exhaust valve needed

[Duncan Charlton]

Tim,

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.

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.

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.

Duncan

On 2/16/15 7:00 PM, Tim Murphy via Fot wrote:
>
> 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.
>
> 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.
>
> 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.
>
> Tim and Ryan Murphy
>
> 1961 TR4 #317 BRG
>
>
>
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