All vacuum readings are in Inches hg. The gage is a mechanical 0"-30"
bourdon type. It has been chcked accurate against the vacuum pump tester
which has a gage.

I made the slide throttle.

The setup  on the a/c now has a throttle body which is acting fine above
the 3000 rpm and giving steady expected vacuum readings of 10-0 "hg
3000-4600 rpm. I am running a fixed pitch performance prop. Below 3000
rpm it does not want to idle and starts surging and shaking.

Compression check gave 100 psi both t1 and t2 w/ schrader valve in.

A previous rx7 non p port engine used to give me 4900 rpm static w/
everything else the same on the a/c so the static 4600 on this different
p port engine is disappointing.

John Prendergast

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You need to take the schrader valve out of the compression tester
as all it does is record peak pressure when the schrader valve is in.
All you need is one chamber working in a case like that.


You should be getting close to 29 inches of Hg at WOT at 4600 RPM.
What does your plenum look like? There is something seriously amiss with these
intake manifold pressure readings.

Perhaps your slide throttle is leaking between the front and rear rotors.
This should not make any difference unless the slide throttle is leaking
all around the periphery. If anything it will tend to average
the pressure.

A couple of questions. How thick is the slide?
Did you use gasket material to seal it? If so how thick is the gasket
material? It is possible to seal the slide between rotors with a short straight chunk
of Teflon O ring mounted in a shallow vertical slot in the cover closest to the
rotor housings .

Not surprising on the static RPM. The torque peak of the p-port
is around 6200 RPM with 24.5 inch runners. How long are your runners?
The torque peak of a side port engine is roughly 4000 RPM and highly dependent
on the exact configuration of the intake manifold. Are you using a 2.17:1 PSRU?

Static RPM is just that. At 65 MPH take off speed the RPM might be higher
but at climb speed of 120 MPH the RPM should be well over 5500 RPM or more.
The p-port is not well suited to a 2.17:1 PSRU. It is primarily intended
for the 2.85:1 PSRU. At 7500 RPM the engine generates 40 more HP than
the best side port engine.

Paul Lamar ...No rotor no motor.

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