That is a comparison between bridge ported (Monster bridge port) and
periphery ported engines. There is no leaking problem. Both stock seal

rings are

untouched. The port area just like the factory periphery port, the port

area will

be filled and no coolant will be available to leak. The port is cooled

buy

inducted mixture while running. As in carburetor ice. After shut down

there will

be heating of the ported area from heat soak.

The kids are driving giant periphery ported engines on the streets of

this

country every night to engage in tire smoking contests. There is no

increased

wear from high RPM operation because there is no high rpm operation in

aircraft

use. Even 7,500 RPM for takeoff is not high RPM. The 300 plus HP from a

12A

periphery port or 330 HP from a 13B is at over 10,000 RPM. That is high

RPM

operation.

The bridge ported engine has much more intake duration and overlap than

a

periphery port, and the kids drive Bridgeport engines to work every day.

It is

hard as hell for me to drive the race car around slowly, with either

port style.

With a 1.96:1 first gear. It goes 70 MPH in first gear. Jump in the car

stick

in 3rd gear and drive to work and back. With a 3.26:1 stock first gear

it is

no problem. It just has very little power at low RPM. You only use 40 HP

to

get to work anyway so how would you know if it didn't have enough power

down

low? My bridge port has 205 HP at 7,400 RPM. We don't use the engine at

that low

an RPM.

If you could only get 200 plus HP out of a junk yard 13B with some pipe

and

epoxy, would that not be worth the effort?

It took me one day to make a set of Pport housings and assemble the

engine.

It is a good idea. It has been done. It works just fine. There is very

little

new ground to cover here. Don't raise the top of the exhaust port at

all. Keep

the intake open duration short and use a wide port to get the flow. It

will

work so well you will not believe it. Even if you miss the tune up, get

the

timing wrong, get the porting wrong, and get the runner length wrong, it

will have

so much power it will scare the crap out of you.

I refer you to Tracy's first take off with the engine turning some real

RPM

where it started to make some of it's potential power with the 2.85:1

box. That

is with a street port not a periphery port.

Not enough rudder? Almost ran off the runway? I like talk like that.
So no full throttle until rudder is effective. Put that on a nice

placard

next to the throttle. Sounds like a P51-C.

Lynn E. Hanover

Lynn,
 The water leakage through thermal cycling I referred to was around the
epoxied PP tube, it may be misinformation, if so  - it's good to clear that
up. It may have come from early trials of home-made PP, that weren't done
properly, who knows, anyhow I accept your experienced  recommendation.

I'm not looking for massive power, I'm looking for a mild street port in a
12A demonstrator to test my aluminium end housings.

So you suggest not raising the port IC from stock timing, to keep the
duration short and the port wide. I'm a bit conservative and am concerned
that too wide a port (especially in the 12A) will cause problems with the
apex seal - so I will not go beyond the width of  the exhaust port for that
reason.

Given my particular situation what IO and IC would you recommend  Lynn
George (down under)

 
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