In a message dated 12/13/2003 2:54:30 PM Eastern Standard Time,
barrygardner@mindspring.com writes:

> If I decided to get more ambitious in my porting, what are the lowest idle
> speeds one can get with a semi-or full bridgeport? Or am I really best off
> sticking with what Racing Beat calls the "streetable" port job?
>  
The idle can be whatever speed you want, but it gets pretty jumpy under 800
RPM. With a big street port, there is little change at all. Overlap between
intake and exhaust is close to stock.  A bridge port makes a big change in
overlap and intake open time. So, it is real jerky under 1,800 RPM. The periphery
port is about the same.

I would start with the street port. A big well done street port is good for
229 HP with 38 MM chokes, at 9,300 RPM.  If you use that for a while, and want
a bit more, you can go back in and bridge port it and go up to 250 HP at 9,500
RPM. Then if you still want more, epoxy the ports and runners shut and put in
a periphery port for 300+ HP at 9,300 RPM.

At speeds that you could use with a PSRU you would have (about) 165 HP-185 HP
and 220 HP. Your HP may vary.  My bridge ported 12A has 245 HP at 9,400 RPM
breathing through two 38 MM chokes and still has 170+ HP at 6,500 RPM.
You will have much better breathing so you should have more HP at 6,500 RPM.
Calculate the torque for these outputs. Multiply the calculated torque value
times the PSRU ratio. Compare that torque figure with the published torque
figures for production aircraft engines. Notice the rated HP of the engine with
similar torque figures.  

Close your eyes, and imagine leaving Sun&Fun vertically.

Lynn E. Hanover