I don't know for the 12A but I do know that there are some very
powerful p ported 12As out there.

 BTW,  for those who want to experiment,  I will be glad to supply the
throttle bodies.  You can bore them to any size you want and place them
anywhere in the housing  you like.  I will be very interested in
reading the reports.      Jerry

 Jerry,
My calculations show with a 20% allowance for turbulence across the
butterfly and parasite drag through the pipes the diameter is 1.75"
Having said that the exhaust out let is about 1, 3/8" max on the 12A and I'm
hesitant to go beyond that width for the 12A.

BTW can anyone give me the width of the 13B exhaust port.

I figure I can make the inlet oblong rather than oval, to make -up the
difference in area lost.

This then brings me to another point. From my observations the opening of
the PP starts somewhere later than the standard port opening ( the the
opening is over the adjacent lower bolt hole).

This may explain why some manufacturers slope their inlet tube to compensate
for that  'bolt hole' restriction and to place the timing as close to the
original opening as possible.

However there is more than enough area on the top side ( as the top adjacent
bolt hole is unused - can anyone say why this bolt-hole is not used?)

Can anyone explain how this affects the timing, or do I have to get a rotor
and shaft set-up to visualize it.
George (down under)

 
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