Jimmyac28

I want to do a carburated rotary swap and I would like to know what engine would you guys recommend I get, I have access to both engines. I will be rebuilding the engines and doing a bridgeport. Whith what engine would I be able to get the most horsepower with?

rx_214

I'd recommend asking Greg at Staff's Auto, he has done racing with both the 12A and 13B.

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lito mazda

You will get more power from the 13b. Carb or not its a 13b has a good 40+ hp more even in its weakest form. As far as the bridge port, 12a's are known to react well to a large bridge port along with a large street port. The way they're made the air flows better than a 6 port 13b. Although the 13b 6 port can also be street ported the ports can't be ported to the extents the 12a can be. Also to bridge port the 13b 6port I recommend doing good research or taking it to an experienced person your working with 6 bridges and position or angle of the bridges are everything.

Jimmyac28

So a 13b with a good street port would work better? What horsepower can I get with a 13B streetported?

lito mazda

All depends on the size of the street port, which rotors you decide to use, what carb you use, the type of exhaust your planing to run and ignition setup. As an estimate I would say with all things taken into consideration with a 6port engine, s4 rotors, mild sreet port about 30-50hp gain and large street port or race port about 50-80hp. Again for the best gains its critical to take all the previous things into consideration. Also with the mild street port the power band is going to be mid rage with race port your power band is going to be on the higher end side of the power band so application or use is also a thing to consider because then even flywheel selection comes into play.