how would a person port or just polish the inner portion(the runners?) of the manifold to try and help flow. dont think of this as a noticable jump in performance, but rather an experiment. i heard early 12a manifolds flow better but they are far more rare and i wouldnt think they would have the same connections for hoses and such(my emissions are removed but there are still some hoses and stuff and i would rather just stay with this type of mianifold because i could get one at the junkyard and use that to experiment on)...what do you think guys, just smoothing it out and polishing should be enough right? or should should i try porting and how would i do that...if i can get a little help then i will post pics and detailed notes....i am going to rebuild the carb and rejet according to what mazdatrix recommends for relativley stock cars...

 

From what I've been reading, polishing your intake is a bad thing. The general concensus here is that a nicely polished intake makes it much easier for fuel to seperate from the intake mixture on carbed applications.

This thread has some better explanations though: https://www.rx7club.com/1st-generation-specific-1979-1985-18/port-polish-intake-604028/

Trochoid gives the simplest explanation:

"If you smooth the intake too much, the runners will wet out with fuel. Some roughness is desired as it will establish a turbulent boundary layer and helps keep the fuel mix suspended in the air charge."

 

wow, that does kinda make sense...i'm glad i decided to ask first...but is there anything we can do to help with the flow of the stock manifold?

 

Search on Sterling intakes and look at some of the pictures. He cross connects the intake holes on the carb mount of the intake. I think Jeff20B has some experience with this as well. You definitely need to forget or ignore a lot of the rules used for port/polishing and matching intakes on bangers as it doesn't all apply to rotaries.

 

ok....i really want to try something at least..maybe i'll go get a manifold and to what t g farrell was talking about...

 

Hey ******** , I'm with them.

 

I had the same question a little while ago, started a pretty interesting debate...
https://www.rx7club.com/showthread.p...light=manifold

 

what would happen if u connected the two ports in the center intake??j/askin

 

that's what i am going to try..but on a "extra" manifold that i have yet to find