Just a thought coz I'm in the process of building a 4port 13B but someone suggested that I just use the 12a intermediate and keep the 6port ends and port out the divider on the 5th and 6ports. I personally wanted to build the 4port with a streetport for more power. Would removing the divider and using the 12A mid plate yield about the same result in power as a 4port? Also what intake would I use if I decide to go with just the 12A mid plate? Any thoughts?

Thanks, Ed

 

I think everything on a 13B is larger than a 12A. So, I dont know if that would work or not.

 

Nope, the end and center plates can be swapped between 12a's and 13B's. Watch for where the O ring groves are, the 6port's had the groves on the cast iron plates, the gsl-se and old have them on the rotor housings. I could be alittle of the mark but not by much.

 

i'm building my SE engine with a 12A intermediate plate... one advantage of the 12A intermediate is that its ports are much larger than the SE intermediate... my SE's intermediate ports were teeny tiny...

 

you are correct, the 86 and newer engines had the gasket grooves in the plates, and smooth rotor housings, which means if you use 86 and newer end plates ur gonna need to use 86 and newer rotor housings too... whats interesting, that i got from atkins, was the rx8 went back to the grooves in the rotor housings... odd eh

 

Also I understood that the rate of failure on the 86' and newer center and end plate grooves was much higher than the older 13b 4port and 12a gasket grooves, is that true?

 

Try to stay away from the NO casting intermediate plates found on Jspec or '80 EGR engines (I can't remember which). I have one of those and its ports are at least as tiny as GSL-SE if not smaller. There are no injector bungs of course. In other words, if it says NO, well, it's pretty self explanatory.

 

i thoguht the 79-81 intermediate plates had as much meat to get ported as of those in the t2's and fd plates?

or maybe what you just mentioned was for jspec models only?

 

Do not remove the divider between the secondary ports and the auxillary ports. It does not help. I have already written paragraphs about why this is so. It is a bad idea.

 

d0 Luck, in the lower right corner you'll notice an EGR cover plate. That's basically all you need to look for in order to tell if the plate is crappy. Or the NO cast in rasied letters by the oil filler tube.

 

In the intermediate housing, why can't you just grind the tiny ports out until they are as big as the larger ports? Isn't that considered part of "porting"? What am I missing?

 

Guys, I dont think I made myself clear. I have 12A plates and SE 6port rotors and housings. My question was should I just use the 12A intermediate plate and keep the SE's 6port end plates or just build a 4 port? I'm trying to keep cost down and by going to a 4port I'm going to need a 4port intake for my Dell. Now if I retain the 6port set up but use only the 12A intermediate plate. What intake can I use? Can the SE lower half of the manifold be ported to match the bigger intake ports of the 12A plate? What about power wise? I'm guessing the 4port would make more ported or net?



Thanks, Ed

 

kleinke, there is less material to support a large port. You'd grind into the water jacket.

13BTOY, I don't know. It's a good bunch of questions.

 

the 6 port allows you to have basically huge ports on the end plates but with a bridge in between, and if you look up rotarygod's post on it, he mentions that with this bridge, when the lower port is closed off by the rotor, you have more intake velocity in the upper port, meaning more air coming into the motor, meaning more power... and yes, you can take a SE lower intake and match the ports... but me personally, i'm using the racing beat holley manifold on my SE engine with 12A intermediate... port matching that is definately no prob, theres tons of extra meat around that thing... and it has larger diameter intake runners than the SE manifold, yet much shorter.... imo a much better combination, and it will also be easy to upgrade to a fuel injected holley based throttlebody in the future...

 

Elysian, thanks for the reply. Where did you get your port design for your 6port?


Thanks, Ed