Lynn E. Hanover

The inlet tract length is a bit overrated as far as all out power goes. It moves the peak torque around, and racers want the maximum power under the curve to be inside of their gear spreads. With a very light car this is a bit less important than with a heavier car. With that bridgeport you will be over 225 HP by 7,600 RPM which will be over 200 at the wheels. My 12A has 221.5 at 7,600, with 38MM chokes. It is a "J" bridgeport.



With a light car there will be less lost to the drive line as well.



The seal groove needs a headless screw installed short of the port, so that the seal will not extrude into the port when the case is torqued up. A dab of silicone around the screw helps the seal. And you want a film of silicone along the outer wall of the groove anyway.



Smooth out the upper runner where it joins the bridgeport. Radius and polish the closing line. Note that the traling end of the side seal is (may be) unsupported where it meets the closing line. The track of the leading end can be seen in the picture in the center of the bridge.



Lynn E. Hanover

C. Ludwig

Thanks to everyone for their input!



Lynn, the port is cut from a Racing Beat template. The closing line on the secondary ports isn't altered from stock. I thought about radiusing the closing line but there shouldn't be side seal issues without moving the closing line further up the iron. Thoughts?

Lynn E. Hanover

Didn't move the closing line? Where is the fun in that?



If you did not move the open line, there is no danger of unsupporting the side seal. Otherwise use a dental mirror and a light look at the assembled rotor assembly and stationary gear turning it with a crank, to be sure.



The leading end tracks well onto the bridge while the trailing end runs well inboard of that, right at the outer edge of the port opening. I got over running rings over sharp edged holes when racing Karts. I just don't do it. So I radius (microscopic if you like) the whole closing line. Mother does not like sharp edges.



Lynn E. Hanover

C. Ludwig

I thought the same thing Lynn. Where is the fun in that? But I decided to defer to RB's knowledge on this one. Also the primary and secondary ports are opened up to the same size. Makes the primary relatively large so it's something of a compromise. It also occured to me that I wouldn't have to worry about the side seal without moving the closing line so...



In regard to radiusing the closing line just for the sake of it relavent to flow versus radiusing it to give a smooth path for the side seal to cross and it comes back on the iron....is there an advantage to flow by curling the closing line gently back? Obviously you'll gain a margin of timing from a large radius but will the radius alone promote flow?

Lynn E. Hanover

I am not clear on what "curl it back" means, but any radius will improve flow over no radius.



Fire up a shop vac or vacuum cleaner. First the bare square ended hose. Listen to the motor RPM.

Slip a foam coffee cup with no bottom, over the hose so as to make an air horn. Listen to the motor RPM.



RPM went down didn't it? Why?



More airflow = more work for the blower motor= less RPM.



It is the same on a flow bench.





Lynn E. Hanover