rexguy

ok guys, i did some searching but came up with nothing. I have an engine with 12a housings and rotors but with what appears to be GSLSE six port irons. I'm sure its been done before, so my question is what do people use for intake manifolds? all I have is 4 port 12a stuff and I would think that any 13b intake mani would have to be shortened to compensate for the narrower rotor housings. I'll try to get some pics up asap, and thanks in advance for any helpful information!

ColinRX7

The coolant seal groove in 13B models are in the iron, and the 12A has them in the rotor housing.



You would have doubled up on grooves?



Or perhaps are the pre-1986 irons (13B) non-grooved?

mazdaspeed7

Actually, there was a 6 port 12A. Japan only motor I believe? Memory is a little shaky though, been a while since I heard about one.



But it may still be a conversion like you said, and someone more familiar with the 1st gen engines will have to chime in about the location of the GSL-SE coolant seals.



Rexguy, what are your plans for the car? Its goign to take some work to get that block into a running state, just have to decide if you want to swap out the irons for 4 port 12A irons, or have a manifold modified or a custom one made to suit the 6 port. Or theres a small chance you could find a 6 port 12A intake manifold that would work. Not gonna be an easy find though.

heretic

Yes.



I would start hunting around in Australian/NZ websites, maybe someone has an intake manifold for some kind of carb for the 12A 6 port. It would be a shame to revert the engine to 4 port status, merely for the uniqueness of having a genuine 6 port 12A, but an engine without an intake manifold is useless.



Stock, these engines had a carburetor and intake manifold setup very similar to a standard 12A, except for the port actator paraphernalia.

j9fd3s

i actually ran across one of these way back when, it was a great learning experiance!



um there is a 6 port 12a intake, it looks like regular 12a 4 barrel intake. engine should make a little more power 120ish/vs 115? and more low end tq.

rexguy

hey, thanks a lot guys, any and all info is greatly appreciated. I was wondering though. I have access to an s4 NA that is shot, and was wondering if any one would think it possible to use the LIM, cutting out a small section to compensate for the rotor width and have it welded back together? after that it would be easy, cause then I'd have the option of FI or Carburation. I just don't know how the runners would be effected in the manifold. If it all came down to it though I'm sure I could find the people and ressources to make a custom manifold. I really would like to try this configuration out just to see what it could do. I'm working on the pics, just have to get my camera back.

heretic

It would probably be easier to make a manifold from scratch than to do that.



Does the 6 port 12A have coolant passages going to the intake manifold? My guess is yes, given that carbureted engines need some manifold heat to have OEM acceptable driveability. If so, you'd have to plug them off at the rotor housing. Then, you cut 5mm out from between the middle ports and the coolant passages, on both sides, and another 5mm from between the coolant passages and the outer ports. Bear in mind, while doing all this, you need to mantain the proper relationship between the actuators and the sleeves, and the outer ports and the flange at the top. Alternatively, you could just hack 10mm from either side and make a new bolt hole for the rotor housing stud.



Then, you would need either a Weber type adaptor, or some way of getting fuel injectors to the center intake ports.



I would be surprised if aftermarket manifolds were not readily available in markets where this engine is more common.

j9fd3s

my memory is that they do have a coolant passage (this is 93-94 though, so its been a while), also the intake bolt pattern is like a 12a so its different from an 84+ 13b, not a make or break thing, but its there

Hyper4mance2k

74-85 13b's had the water seal in the rotor housing