so far all ive found is that the second biggest stock port irons are the third gen irons, then the biggest stock port irons are the 2 rotor cosmos irons, ive already got the ceramic 3mm apex seals, and am now looking into which irons i should persue. ive got a good s5 core motor to get the e shaft and 9.7 rotors from, and my goal is to make the absolute most power on a street port, its going to be run on a carter series carb and the racing beat 4 port 13b intake manifold, because thats the way i want to do it. i dont want or need any comments about alcohol injection or webers, so if thats all you have to say then please keep it out of my thread. id rather not have to buy and entire core motor just for the irons, and i plan to run this motor for a very long time, thats why ive decided to use my ceramics not in mega bridge or pp. the reason i want to start with as big a port on the irons as possible is so that when they are ported i can make the most power.

 

the FD center iron is bigger than the cosmo, its the cosmo end irons that are bigger than the FD, so the biggest stock port set is cosmo ends, and FD center.

but since you're porting anyways, i'm not sure it matters.

if it was mine i'd rather do 2mm seals instead of 3, but everything else is good.

 

it doesn't much matter what you start with. you're porting it.

 

I may be a little of topic . but what about the 12a center iron. Its has a pretty big stock port to..

 

I would do an FD complete set simply because of availability. If something were to go wrong it's easier to find FD irons than cosmo irons. Just my $.02.

 

Very True. Just find yourself 3 FD irons and call it a day. You will make great power on a street port with those.

 

4-port 13B manifold won't mate up to FD or Cosmo engines, you'd need one made for a FD or Cosmo. They use a weird bolt pattern different from anything else, 4 port 13B are just like long 12As (because they are).

Check this page to see the differences: http://www.mazdatrix.com/c-2.htm

This bugs me because I am putting together a 4 port 13B out of GSL-SE and late 12A parts, and I want to use a manifold that has a Turbo II flange, but it is a no go unless I only attach it with the rotor housing studs. Not enough metal on the 12A end housings to drill new holes, so they need to be built up first. I am going to try brazing on some junk housings to test building them up, but when that doesn't work I will end up buying some aluminum and whittling up an adapter plate.

 

Massive porting will not necessarily make massive power. Try not to go overboard.

 

I have an adapter plate to do what you want. You want to put a TII pattern intake onto an early 13B?

 

That is exactly what I am looking for.

I expect that I could fabricate one for less than shipping would be for one, though, let alone how much they cost. For some reason, all of the interesting adapter bits seem to come from your part of the world

 

Bigger is not always better. Not that you want to hear it but your going about this the wrong way. If your limited to the one intake option you need to ask what type of porting will allow you to get the most out of what the carb/intake can get you. Your header is also part of the equation on the "most power" as many of us know all headers are not created equal. and we can't forget about proper tuning. Thats a whole different post.

Best of luck to you.

 

Being one to do stupid things all the time, I'm not one to deter someone from doing something just because it's a bad idea. Making mistakes is a great way to reinforce one's education, as long as you're willing to learn from those mistakes.

I mean, if you wanted the LARGEST side ports, you'd start with pre-FI tallport center housings, and 6-port end housings with the two ports opened up into one gigantic port.

The thing is, there's a point where closing the port later just hurts you all around, same with port sizing. That seems to be why the 4 port housings are just so much better than the 6 port even though the 6 port housings have more port area and much more port timing. They close too late in stock form, and there's so much area that they never really get moving until after the engine's other flow inadequacies choke power off.

You can find pictures of absolutely gigantic ports all day long. The subtext is that these ports are always on housings that look like they've been sitting under a tarp for a long time, almost as if someone tried them and found that they sucked.

 

Not to sound like an ***,but you are selling all of your mazda's.you have changed your mind so many times and haven't done any of them.pick something,get it done and enjoy it.