Thinking of going the precision engineering short crank kit route for a 3 rotor build, I know mostly all short cranks run them peripheral ported since you are blocking up the irons so the 13b smaller iron port sizes do not become a factor. My question is do I have to run the short crank as a peripheral port, or can I get away with running the motor with a semi p port and to make up for the iron port size difference I could run (2) 12a irons that have larger ports than the 13b, just not as large as the 20b fat iron. Any help would be appreciated

 

yes you can still run them with side ports. you don't have to go semi pp

 

Non fuel injected pre-86 have primary and secondary ports about the same cross section area. The first short 3 rotors I have seen were built out of 12A/4-port 13B (same thing) end and intermediate housings and 13B rotor housings.

When Mazda put injectors in the intermediate housing, they made the primaries' CSA a lot smaller.