I want to rebuild my 12a and if its possible make is a 13b but I dont know if I can or not. but non the less. I heard you need a special tool to put the motor back together. is this true. and if it is where can I get this tool and how much is it

 

iv never heard of making a 12a a 13b. i mean i guess u could port it...and fuel inject it...but its still a 12a. and if ur gona do all that...just buy a 13b. but then again y? carbs are cool. i too are rebuilding a 12a (comes in tomorrow actually search around maybe ud like to do a nice rebuild..and turbo it and keep the carb...thats wut im doing....just hang around...read some stuff...ull get more outa that then everybody just tellin you things here and there.

 

Making your motor into a 13b would mean replacing most of its parts with those from a 13b and the end result would not have much if any of your original 12a left in it. If you read how the engines are put together this will make sense; particularly note the rotors are wider, hence wider rotor housings, with longer eccentric shaft, etc.

 

ok that is what I thought but thought I would give it a shot... I will prolly have to get new housing anyways since I smoked an apex seal. I think it pretty much destroyed the housing... do the side housing still work with a 13b... I thought about just getting 13b housings and I Guess an exxentric shaft as well since I will need it but i want to do a carb 13b not FI

 

Yes, you can use the 12a side housings with the remaining parts being 13b, as long as the 13b is from an 84/85 SE. The reason why you need the SE parts to do it is because Mazda moved the grooves for the water o-rings from the rotor housing to the side housing beginning in '86. This combination will give you a 4 port 13b.

You would need a different intake manifold and maybe carb as well as a different exhaust manifold, etc. If you want a 13b, it would probably be best to get a complete engine, rebuild it if needed and install carb, intake manifold, exhaust manifold, etc. The carb setups normally do not take advantage of the 6 port setup, so it would be best to either:

1) use an SE engine with 12A side housings (to make it a 4 port)
2) get an early 13b engine (already 4 port)

All of these options require a different engine mount or modification of you current one. There are also a couple of possibilities for using 2nd gen engines, these also require an SE oil pan and changing the front cover.

Kent