I'm in the process of building a RallyCross FB. The engine is more or less stock. I've opened up the exhaust a bit, pulled some stuff off, but that's it.

In the Spring, I'd like to replace the carb and intake manifold. Long term, I'd really like to port the engine.

I would like to go with a Weber 48IDA. Does anyone know what the largest port I'd be able to get away with while using the 48IDA? Racing Beat says they sell a 13B Peripheral Port manifold that will fit the 48 or the 51 IDA. I would think the 48IDA wouldn't supply enough air and fuel for a peripheral port, but I don't really know. Is it capable of it? Or are they just advertising it this way because it will fit, even if you wouldn't want to use it. Most likely, I'll go with a large street port, but if I'm feeling ambitious, and if I have a spare engine (which I may), I would like a peripheral port.

Any help would be appreciated. Thanks.

 

Good luck if you try to build your own peripheral port.

I would suggest the 48 will be too small so go to the larger 51 or 55IDA. Twentyfive years ago when the RX-7 was first seriously raced, the output was 290hp for an endurance race engine and 325hp for a short course engine. They should still be your targets now for a NA set-up.

Have a look at some of the info on the Rotary Performance forum, several people who post there have gone down the pp track.

 

pm, 680rwhp

Robert from Rotaryshack

 

Going larger than the 48 will indeed get you a bit more hp but the 48 should be fine. I am using the 48ida with my 12a peripheral that should be finished shortly.