12A?

Okay, what are the types of rotary engines, and is one really better than another? I'm asking because I found a CL listing for an '85 RX-7 with a 12A rotary. I can afford to buy the thing to part out, but is the 12A worth it? This would save me time finding the rear axle and transmission also.

I can help a little I hope. For the most part(there are exceptions) the 12a was carbed and not a fuel injection engine. The 12a is smaller and produced a lot less power than the 13b which is also typically fuel injected. In 1979 Mazda introduced the RX-7 in the states and put the 12a in it. there were a few changes over the years, but nothing that made it that much better or worse. In 1984 Mazda introduced the 13b into the RX-7 GSL-SE. It had much more power, the fuel injection was a step up as it eliminated the cold start and hard start issues of the bulky, and smog equipment covered carb that Mazda was using. In 1986 a slightly upgraded version of the 13b was introduced in the 2nd generation of RX-7. It had even more power and later was offered with a turbo option.

I have a 12a installed in my 1989 B2200 and I will say it has more power than the 2200 or the 2600i, but it is definitely a dog compared to the 13b power plant. I used the transmission from the donor 1985 RX-7 as well, but not the rear end as it a 4 bolt lug pattern and narrower than the B2200 rear end. I had to fabricate the motor mount and modify a header to make it fit. I then trashed the carb, intake, and smog pump and threw an aluminum intake on it with a Weber DCOE 40mm. this was an improvement, but the 13b still has it beat. If you are looking to simply do a cheap motor swap the 12a is a great option. If you want the extra power and fuel injection then the 13b is a better deal for you. Neither of them is any good for towing, so I would not do that, but not many people tow with a b-truck. Let5 me know if you have any more questions and if I need to clerify anything else for you. Good luck. -Ed

Okay, thanks. So is there any difference in carbs between a rotary and conventional engine? I have a Weber 34/34 in the truck already, but it died out. I was hoping for fuel injected, but this is a fast chance to get started without too many more delays.

So, the transmission didn't bold right in to the existing mounts? I was hoping for that. Also, what about the header? Is it different also, or would I be able to hold onto my Pacesetter I have in the truck already. Otherwise, what else is involved?

Well, nevermind. I found someone selling a 13B Turbo S5, along with the 5-speed tranny, ECU and just about everything else. Is it enough HP on that to require replacing the rear axle, or should I still be set?

it ool will hol up fine

Sweet find, and the transmission did bolt right in on mine. I have heard that the 13b tranny fits even better. I would try the stock rearend and hang onto the rx-7 rear until you come to a conclusion.

Yeah, I went ahead and bought the 13B. I don't know how long it'll take to ship here, but it'll work out with my corrective eye surgery this week. Let's hope the transmission will bolt in, that would make things much easier. Hopefully I won't have to search for a rear end later down the line, but that's not too expensive anyway.

One more quick question. If this transmission is from the RX-7 and I use it to replace my automatic, will it still work with the existing driveshaft and everything also?

Mine worked perfect.

Sweet. Thanks for the help everyone.

I'm looking into a rotary swap as well. I'd prefer a 13B, but I'd probably go carbed with it.

I'd actually basically like to make an RX7 pickup. Would love IRS with coilovers all around. I want to build a low and fast B.