Im picking up an 80 engine and tranny from a buddy but he is keeping his lightened flywheel so i need to get one on there but am a little short on doe to drop on an aftermarket flywheel w/counterweight. I have heard the 81-82 12a had a 22lbs flywheel as opposed to all others years around 27+lbs is this true? will it be ok to use on the 80 engine? please let me know asap and thankyou

 

It should be ok. I've been contemplating this very swap myself. I say it should be ok because if you look on Mazdatrix, they list the same rear counterweight for '79 through '82 so we must assume it works with the front counterweights of '79-'80 and the slightly different looking '81-'82 type.

That's one point of view. Here is another. I've never gotten a definitive answer in all these years as to whether you have to change the front counterweight from the half circle '79-'80 type to the weird looking '81-'82 type when swapping the 30 pound '79-'80 flywheel to the lighter '81-'82 flywheel. You probably don't need to because the rotors are the same weight, and you can use the same rear counterweight... so why not?

One final thing. I'm doing a rebuild on the engine now so I can use which ever front counterweight I want. But keeping things within the realm of stock, I think I'll choose the odd looking '81-'82 type because I'll be using the '81-'82 flywheel.

 

I'd be interested in a definative answer as well. The 84 I bought had a pre-84 motor in it (no T below the oil pedestal) However, the motor had a chewed up rotor bearing and the front/middle irons were scarred from the side seals being bad on the front rotor. This motor had the "lighter" flywheel on it as well, but not the different front counterweight. I have no information from the PO as to what all was done to this motor, but it makes me leary of trying what you speak of.

 

So I have the option to pick up a 1981-82 23lbs or the 30lbs 1979-80 flywheel both for $50 shipped to me. What do you guys think about the 23lb on my 80 engine? I had a look on Racingbeat and the listed their counterweight from 74-82 so even though the flywheel is 7lbs lighter then a 79-80 its still counterweighted the same? sorry for the elementary questions I just dont want to screw a good engine.

 

Yes, it is still counterweighted the same.