Actually there is a big problem with trying to swap Cosmo or even FD housings The exhaust manifold studs don't line up! I talked to a guy on the phone about this and he told me there will be a tiny red or blue line between the sparkplug holes on the right side of the housings. If you put them both on level ground you will see how one stud is higher than the other! Whoa! Stupid Mazda engineers. They either did that for money or so you wouldn't mess up the ACV ports or whatever they are down by the exhaust port.

 

could you swap s4 and s5 rotor housings or is there a difference? I know the rotors are different.

 

S4,5 & 6 housings are basically the same but with detail differences on the outisde of the castings. Below the spark plug holes, some have a sharp edge on the housing face and some are smooth. S4 & 6 tend to be smooth and S5 come either smooth or sharp. Photos show this below. Also included a shot of two 12A housings with EGR ports on opposite sides for F & R. They can be drilled out on the other side if you need to swap a F for a R and vice-versa...



Sharp:

 

Smooth:

 

Old 12A's with handed EGR ports (which can be drilled out on the other side where there is a provision already in the casting for it)

 

thxs for the pixs, I have never seen that "sharp" style..

 

is there a difference in the gap between leading and trailing spark plug holes between s4 and s5?

 

I have an s4, engine to my knowlegdge has never been rebuilt. I have the sharp housings. Any way to explain this?

 

i've never looked



mike

 

There has got to be some way to tell what rotors came from what type of motor, wither it be an N/A motor or TII, S4, S5, or FD. Is there any type of mark on the rotors? I know there is a weight stamp, but I don't recall what he different weight stamps are.



I propose that we make a list of what the different weight markers mean and how to tell the difference between the different rotors. I think it would help me out as well as others.



Chris