i know theres the turbo 12a that was a japan only thing but i was at the atkins web page and saw they listed 3 different motors 79-80 81-82 and 83-85. what makes them different and which one do you gods of the dark side belive is a better motor. i plan on buying a new motor and super charging it. i plan on keeping my old motor and rebuilding it on my own ect. maybe keep it for a spare or build that rat rod truck me and my buddy want to make.

 

They are classed that way because of engine rotor weights. For balancing purposes when using a stock flywheel.

79-80 also had different exhaust ports for the usage of the thermal reactor.

 

Yea,the 1st gens had slight changes to the 12A over the years,but it didnt amount to a whole lot.The HP didnt change at all,and the lighter rotors in 83 were accompanied by a heavier flywheel,so that didnt really do much either.

In addition to the 12AT,there was also a 6-port induction 12A in Japan.A curiosity at most,they are rare and not really worth anything since they supposedly have very small ports.

 

There's also the pre-79 12As, some had a twin dizzy and iirc, the very 1st ones had 6mm apex seals, or am I confusing that with the 10As? There is also a variety of intake ports, different castings for the irons and the very early housings had 3 holes for each exhaust port instead of the now common single one.

Starting from scratch, I'd opt for a 4-port 13B streetport. Whether it be an SE 13B with 12A end irons or a 2nd gen TII block with NA rotors.

 

ding ding ding....

technically:
12a= twin dizzy thick apex seals models sold between inception and 1973 or 1974...
12ap= newer version with narower seals used in rx-3~all pre 1979 sa22c cars
12at = turbo version sold only in japan in the cosmo and rx-7

many people are not aware that all of the engines that we call 12a's are actaully 12ap models. I have had many arguments with people in the states about this, but the twin dizzy version was substantailly different in many aspects very primitive compared to the 12ap.

kenn

 

I just took apart two 12A engines, and one thing i noticed immediately was that there was a difference in the location of the tension bolts. The Haynes manual disagreed with both blocks. Most were same, but there was a difference in the high port side. Any ideas/explinations? Forgive the rotor newbie.

 

thanks guys.

 

i did not know this. what does that designation mean? i thought they were known internally (and unofficially) as the 12B engines. can you elaborate or clarify?