For a purely performance gain, again I think that going to the larger carb
is of more benefit. Actually the smaller dia runners would just increase
the velocities at lower rpm's keeping the fuel in suspension as it were,
and helping in the emission dept at those speeds which is probably one
reason why it was done. Actually the "log" manifold isn't all that bad as
far as flow. Look at any late model fuel injected intake and you'll find
something very similar. Granted that fuel in suspension doesn't like to
make sharp right turns, but it does so fairly well in this case (possibly
another reason for the smaller runners. One would have to do a flow
analysis at 6000 rpm velocities, and while there would be some difference
because of pumping loses, I still contend that the carb with its 1-1/2 dia
bore will be the limiting factor at higher rpms - kinda akin to what NASCAR
did by limiting the orifice under carbs to reduce top end hp. While doing
so under the premise of the "smog" police, the 175 carb looks identical to
a 150 outwardly so it would probably pass the visual unless the operator
knew what to look for. The mounting flange is slightly bigger (I believe)
but the main difference is that the 175 has a 4 mounting hole, square
flange and the 150 has a diagonal 2 hole mounting flange. It could be
tuned just as any 150 can, and connected to smog equipment in the same
manner - A manifold could be modified fairly easily, by removing the
existing flange and welding on a new one, remachining the bores and
mounting holes etc. and one could even smooth the weld and nobody would be
all the wiser - Heck there may even be enough of the existing flange that
no welding and very little machining would even be required to adapt a 175.
Barry Schwartz (San Diego) bschwart@pacbell.net
72 PI, V6 Spitfire (daily driver)
70 GT6+ (when I don't drive the Spit)
70 Spitfire (long term project)
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