Fist off, i just purchaced a 1985 gsl with a 12a that had been swaped in to replace the origional dead 13b

The i know the 12a seems to be good for 100hp

the car has a straight through 3" exhaust, no cat, no resionator and a muffler i can look straight through, how much hp can i expect the exhaust to add?

secondly what basic mods can be done to the 12a to increase its power? ive heard things like porting exct, but what can be done without opening up the engine?

Thanks,
- Bochek

 

GSLs came with a 12A, GSL SEs came with the 13B. I suggest you spend some time reading the FAQs. 3" exhaust is too big for a stock port 12A or 13B.

 

2.5" is really all you need on a 12A.... 3" will just make more noise.

Either way,the exhaust isnt going to be worth much power without headers.A full system with headers and a good muffler would be worth about 15-20HP......not much,but its critical to do the exhaust so you can reap the benefits of the other mods.Things like an MSD direct fire ignition conversion and a performance carb will work with the exhaust system and allow you to hit about 150HP without opening up the engine for porting.If you do port,the sky is the limit,although the powerband will move up in the revs and idle quality/fuel consumption will suffer.To keep it civilized and streetable,the 180-200HP mark is a good comprimise, when porting for power on a streetcar.
Also......a light flywheel,while expensive,is a great mod on any rotary.The stocker is very heavy and keeps the engine from having the dirtbike-like throttle response that it should.

 

FAQ can answer a lot of your questions
https://www.rx7club.com/1st-gen-archive-71/1st-gen-rx-7-faq-page-507782/

 

Where abouts in ontario do you live?