Hi Folks, glad to see Joe heard "The Sound" when my Ardun went by his
Timing Stand at Maxton. I have always thought that part of the charm of
motor racing is the exhaust notes of the four-stroke engines.
All it takes is eight straight pipes on a V-8 (I know, some will say
"but modern practice is four into one on each side"). I copied my
exhaust system from the factory racing Vincent Black Lightning pipes.
They were usually 2" x 44", but I possess a set of originals that are 2"
x 48", which would have been intended to broaden the usable power range
a little, rather than have the engine suddenly come to life at 4000,
and peak around 6000.
So I made my exhaust pipes 2" x 48", one for each cylinder. The results
are nothing brilliant, 131+ in the standing mile at Maxton, but for a
239 gas Ardun it means the engine was doing about all that could be
expected of it in a hiboy roadster. It suggests to me that no other
form of exhaust system would have done much more. I won't go into the
head wind, the rich mixture, the wrong gearing, etc., just try to do
better next time.
What, you may say, does a Vincent Black Lightning motorcycle have to do
with an Ardun? The answer is, that the valves, porting, compression, cam
timing, intake system, and cylinder size are not as much different as
you might think, so both kinds of engine may like the same kind of
exhaust system, as evidently they do.
I think I've told you before, that a privately-owned Vincent Black
Lightning (Burns and Wright team) set the official (FIM recognized)
World's Motorcycle Speed Record in 1955 in New Zealand at 185 mph, and
held it for a while, until somebody else upped it. This was with a pair
of the 2" x 44" straight pipes on the 1000cc Twin.
So let's "hear it" for one straight pipe for each cylinder on our
four-stroke engines! Cheers from Ardun Bill in the Great Dismal Swamp,
Chesapeake, VA
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