Engine swap help (counterweights)
 

im getting ready to swap my engine out for my new one
my engine currently is an 83-85 12a
the engine goin in is a 79 12a
i have an 84 flywheel on my car with a gsl-se clutch
ive heard the counterweights are different from 79-82 and 83-85
the question i have is in order to use the flywheel and clutch i have (resurfaced flywheel and 90 percent life on clutch)
will i need to swap the front counterweight to be able to use the clutch and flywheel, so everything is balanced properly, or will the 79 front counterweight be fin to use with the 83-85 clutch/flywheel setup?

thanks

-greg

the front and rear/flywheel counterweights are matched to the rotors, so you should use the 79 flywheel on the new engine.

damnit, i want to use the 83-85 flywheel because it is resurfaced and the clutch is damn near new
and i know the clutch wont fit on the 79 flywheel
are you sure switching the front counterweight as well wont allow me to use the 83-85 flywheel?

-greg

Nope the weights are specific to the weight of the internals. :(

GRRRRRRRR :mad:

so what will happen if i use the 83-85 flywheel and clutch?
bad vibrations?
-greg

Cmon now how hard can it be to just do it right the first time? The alternative is to put it together and tell us how long it lasted before it beats itself to death.

how bad are the rotors on the 83-85 engine?? I'm assuming that you're swapping motors becasue one of them is shot but depending on the damage you might be lucky enough to salvage the rotors themselves from the 83-85 motor. If thats the case, you should be able to use the 79 housing with the 85 counterweight,flywheel, rotors to suit your needs.

no both engines run fine, im swapping my 12a for a ported rebuilt 12a from an SA

-greg

Even though that SA engine is ported, it may not rev as quickly as you'd hope. That's due to the heavier rotors.

mazda switched to a larger flywheel as they used lighter rotors on the 84-85. old ones have heavier but smaller flywheel. If I were you, i will stick to the 215mm flywheel. and hard or how fast it will rev will depend on your port. heres a solution: buy my extra 215 aluminum flywheel. ;)

also, Im not sure if you can use 13-B front counterweight on a 12-A engine.

You can't use 13B counterweights on a 12A.

wackyracer how much u want for the alluminum flywheel
pm me

-greg

greg
pls check your pm.

thansk

You can get away with it as long as the front and rear weights match. There may or may not be a slight vibration - nothing major. I've only done the lightest rotors with the lightest flywheel combo before. The experts tell me it's the same story on the heavy rotors and slightly heavy flywheel.

Staying with just stock parts: ideally you'd want the 81-82 flywheel and front weight - they already match the rotors, are the second to lightest stock rotating weight for a 12A, and will rev faster than the lightest stock rotating assembly because of weight distribution. You can even bolt your larger clutch to the 215mm flywheel with a little extra work.

please explain how i can use my gsl-se clutch with the 79 flywheel

-greg

If it's not a high performance (high dollar) clutch then I wouldn't bother. But if it is you can go about it two different ways - spacers between the pressure plate and flywheel along with longer pressure plate bolts along with machining out the inside of the flywheel surface to approx 235mm (this is the setup I use). Then option #2 is machining down the surface of the flywheel so that the pressure plate and disc mount as they would on the later flywheel. I havn't tried the latter yet, but in theory it should work even better than the former.