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January 02, 2005
Mitch..IMHO....
if you are going to use the Judson, I would
call APT and source the best quality valve
they have to offer. Otherwise, unless you've
got a hairy cam in there or are running
10.0-1 or a higher static compression ratio,
standard quality/design should be fine
normally aspirated.
About oversized exhaust valves....many moons ago when the first 1275 Cooper
S
types came out, they went with a larger
1.4 intake valve and subsequently, went to
a larger than stock exh.valve to "match", feeling this would give more powe
r. It
didn't. What it did do was lead to cracking
of the casting between valves. So, back to
the stock exhaust valve while retaining
the larger 1.4 intake valve.
The point is the larger exh valve, even when "matched" to the larger than
stock
intake valve did nothing for power.
Bearing the foregoing in mind,
were you to use the Judson,
upsizing of either valve could only increase
flow capacity....but only under boost. And
considering the effective "dynamic" CR
under boost (with attendant increase in
combustion temperature) the best quaility
valve (s) would be the way to go of course.
With boost, I wouldn't be worrying about
exhaust gas reversion any more than I would worry about it with near stock
cam timing. Once the timing gets to that
of a VP3 or Kent 286 (most expecially with
larger intake valves) I would certainly consider anti-reversion valves at t
his
point for the sake of the low end.
Cap'n Bob
'60 Frog
"Robert E. Shlafer" < PilotRob@... > 35519
Posted on January 2, 2005 06:09 AM
Posted to category(s) Cylinder Head | Engine (external) | Engine (internal) | Exhaust System | Forced Induction | Fuel System | Gauges | Intake System | Miscellaneous | Restoration | Technical Info | Transmission | Tuning
