I hate doing this, but I have been put into a time crunch to get my 79 on the road kinda unexpectedly and I need to know if the FD exhaust mani to engine gasket will work on my stock 79 12A. Pictures on Mazdatrix are inconclusive. I will likely end up using these with the RB header I picked up, so the extra ports aren't all that important, just that they are sealed. If anyone could give me an answer on this, I would appreciate it. BTW, tried searching but turned up nothing on the subject.

 

No, it wont work. Center to center spacing of the exhaust ports is different due to wider rotors than the 12A has (rotor housings are thicker)

 

This I know 83Limited, but the FD gaskets are individual and not connected in the center, so the width will fit. My big question deals with the bolt spacing and port size I think. I don't think the port size will affect much, its at least the same size.

 

Cut the flange and them trim,i always use 13-b gasket if 12-a is not available

 

Buy a 4-port 13B gasket, cut the center out, bolt it up and drive. Your Mazda dealer probably has one lying around or can get them faster than anyone else. It'll work and cost you nothing more than a few minutes of cutting.

 

the FD ones will work, cause they are separate

 

On a 79 12A aren't there some extra holes going into the exhaust ports that you
need to make sure are sealed up? Just make sure whatever gasket you use covers
that so it seals, or you will have large exhaust leak.

 

^Thermal reactor air injection holes. I'm not sure about FD gaskets covering the holes completely. I've got these parts I could test fit, but they're kinda buried in the pile. Maybe I can later today.

 

I'm an ***. I completely forgot my engine was built with REW housings, and I just bought an fc gasket to put on it, which when cut in half will fit a 12A. So the answer is yes an FD gasket will match up to the bolt holes.

 

Well, an FD gasket matches the bolt holes properly, but on a 79 there are two ports below the main ports that the FD gasket unfortunately does not cover fully. I am not fully sure what these ports are for, but I believe they should be covered regardless of their function.