The HS bodies are long and the early manifold is short. Conversely, the HS6
is short but the manifold is long. Measuring from the face of the head to
the outer face of the carburetor, you get the same dimension. However, I
don't know what happens with the air cleaner to inner fender well clearance.
I also find it interesting that you can make the early "short' manifold
flow nearly the same cfm as the late "long" manifold. I do them but I have
to charge $300 for it because it is so time consuming. Now, if we could
just get rid of the jet bridge in those SU's, we could make the intake
system flow really well, but to the best of my knowledge nobody has found a
method to do it and still have the car driveable. I tried it one time, but
the engine would only run over 3000 rpm. Kind of a fast idle. It went like
stink on the top end, though.
I also tried the bridge modification outlined in Vizzard's book about the
BMC "A" engine and although it flowed better on the flow bench, the carb
just wouldn't pick up fuel from the modified bridge. My guess is that
Vizzard tried it on the flow bench but not on an engine with fuel in it.
uncle jack
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