Ok so I'm thinking about cleaning, stripping and rebuilding my 83 carb and putting it on my 79 engine. then I got to thinking about porting the intake. I did some searching and from what I understand its best to leave the primary exits stock and only porting the secondary exits and all the inlets slightly but polishing is bad. is that correct? Also what about the single butterfly that’s in the intake mani? What does it do? do I still need it if all my emissions are removed? and can still port the hole that its in?

 

Porting is always good. But thats as long as you make them flow equal. The butterfly is whats called the shutter valve. It closed during deceleration to prevent shuttering. IDK if you would be able to port that sucker out to match the other. If im correct if you are able to pick up a RX4 12A intake, It flows much more than these. Other wise you could probly make one urself if ur able. I think it would be too much work to Port that stocker one to do any good

 

rx4 intake mani huh? ill look into that. from what found on here you can benefit from porting the intake in the mid range but if you polish it’ll make the air and fuel separate or somethin.
thanks

 

Im sure theres mixed opinions about porting and polishing all over the place. V8 guys have been doin the porting and polishing for many many years. I can see keeping some turbulence in there to keep the atomization consistency. But gettin the RX4 intake will take some headache out of it. As long as ur able to get it at a good price. im thinking of doin a custom intake for my 12A, But thats because im the the 3rd gen twin setup and it may not clear the stock intake. Ill find out when i get to that stage but as far as runner length. Its not gonna matter on a boosted engine. If that where you plan on going some time.

 

The RX-4 had a 13B and Hitachi carb. It would be a lot of work to make it fit your 12A and a little easier to make the Nikki fit the manifold. Opening up the intakes runners a bit will help flow, but keep them rough to maintain fuel atomization. You can remove the shutter valve. It's purpose is to eliminate backfiring on deceleration. The 79 RX-7 12A manifolds are reported to flow better than the later manifolds since there wasn't as much emissions crap on them.

 

I've heard that as well. SA 12a manifolds flow better than the FB 12a manifolds....

 

K I have a black and decker rotary tool. I can use that to port the intake mani right? If so what kind of attachment would be best to use?

 

Do a search on reversion. When you port you don't want to lose the reversion completely.