This is some interesting discussion, I just want to remind everyone
that the vertical dimension of the peripheral ports affects timing, so
when you increase diameter you are mixing effects of timing and port
size.  This is why the factory ports are squared off, you get more

port

area without affecting timing by squaring off the port.

Paul, I think you are on the right tract with the idea that the intake
tract is more important than the area of the port, not counting timing
effects.  What I mean is if you had a 13B with x HP and round ports,
you could square off the ports, increasing their area without changing
the timing and you would have more power than before.

Hans

One more reminder - make sure that the apex seal is supported as it
passes over the peripheral intake port.  This means that the 'small'
piece of a 2 piece apex seal will not extend into the  port at all and
that the 'long' piece of the apex seal will completely bridge the port.
A one-piece seal would make this less of a concern.  The idea is that
the apex seal will be supported on both ends as it crosses over the
large open face of the peripheral intake port.  Also remember to chamfer
the edges of the port after all port work is complete.  I do not plan to
make my ports completely square:  the upper edge will be slightly
rounded (like a 'smiley face') to help ease the transition from the open
port face to the support of the rotor housing wall.  I will probably
make the upper edge of the intake port similar to the shape af the upper
edge of the exhaust port.

Ken Powell

 
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