Since I'm concerned about the size of the hole in the rotor housing I
thought I might try a smaller hole (about one inch diameter) along with
the regular intake holes.
    I sliced the manifold about two inches back from where it mounts on
the engine and knocked out the freeze plugs and hogged out a bunch of
the inside, as per attached photo.
    I will seal the center divider and adapt it for the slide throttle and
injectors.
    Do you think it will help, or hinder???
Hurant Karibian


Is that cast iron Hurant? I don't recognize it. With a one inch hole
in the rotor housing you won't notice the HP increase.


Paul Lamar ...No rotor no motor.



Hurant, I have done this myself. I still have the home made manifold in my
garage. I've made this port as large as 2". I made the manifold runners
operate only two side ports on the primaries and the two other side ports
and the peripheral were operated by the secondaries (carburetor days)
I had a decent idle and killer WOT. This port alone will boost you about
75hp.

Bob Mears

The key words here are the two inch p-port holes in the rotor housings.
Not one inch. Richard Sohn recently tried the idea again on his one rotor
and he
said just use the 2 inch p-port and don't bother with the additional side
ports.
Especially for an aircraft engine that never sees anything below 5000
RPM.  Now if a super smooth idle is necessary such as a sea plane it might
be a different story.

Paul Lamar ...No rotor no motor.


Actually, one inch will increase HP. Its not the size of the hole for fuel
flow that increases the HP, its the intake port timing. That port will give
several degrees of overlap timing (At one time I knew the exact #'s..but
that was 20 years ago)
With the right exhaust system one exhausting rotor will scavage the other
rotor, and pre-start the intake charge well before the rotor has to suck in
its own charge. There's the HP.

Bob Mears

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It is also the size of the hole. A two inch hole will flow four times the air
as one inch hole will flow. Area = pi x radius squared

One hole inch area equals .785 square inches.
A two inch hole area equals  3.1416 square inches.

If it were not true there would be no point in these p-port
rotor housings.

We just got done dynoing a 2 inch hole p-port engine.
Mark has the engine and will soon start it up installed
in his Mustang II. We got over 240 HP with a Weber 58 mm
from 6800 RPM to over 7300 RPM.

Paul Lamar ...No rotor no motor.

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