rithsleeper

Diablolical just told me in another post they are not interchangeable. Since it was way off topic of original post I wanted to get some more input (no offense diabolical1 I believe you).

I want to know what my best option would be. My race engine from my 79 is toast. I have another 12a from a '85 that is in good shape I am putting in. I'm not sure but it looks like I have a lighter than stock flywheel on the current engine, my clutch is in great shape, and the trans has miata internals (so I'm told). I want to just use the long block from the 85 engine and reuse my carb, water pump, clutch and everything even the oil pan from my current 79. How can I do this or is it impossible?

Why can't I just take my clutch, and flywheel, and whatever counter weight is there and slap it on the back of the 85's long block and throw it in? What do I have to do special?

diabolical1

iTrader: (3)

simple answers:

the issue with flywheels is balance.

the issue with clutches is size.

that said, you didn't mention that you had an aftermarket flywheel in the other thread. it makes a difference because all you'll need is the appropriate rear counterweight and you can keep your flywheel/clutch. if it's a case where you're unsure, post a photo of it when you get the engine out.

https://www.rx7club.com/1st-generati...estion-984008/

also, no need to change the oil pan or water pump.

oh ... and no offense taken.

rithsleeper

Well here are the pics. Reason I want to transplant the water pump is the thermostat is drilled and I know there is no rust in the system cause I flush all the time, the oil pan is a high volume pan, and the distributor is new and contacts all clean.

I found a "31" marking on the '85's flywheel, and something on the '79's but couldn't make out what it was so I took a pic of it. looks like a portion might have an 8???


this is the 85

this is current race engine ('79)

this is only markings I can find on the 79....


So I take it the advice is use the clutch that came with the '85 and hope it's in decent shape?

KansasCityREPU

iTrader: (9)

This will help you with understanding the flywheels and clutchs.

Flywheel and Clutch Explanations

Flywheels

rithsleeper

I read all these already and all it did was say it was possible.... but it simply says "let us know" and we can make it work. Well I want to make it work..... so is there a counterweight if I get the flywheel off that I can transfer over? I don't have much more time to doddle on this. I have tomorrow off then work for a while.... its tomorrow or never since I have another race in 3 weeks....

Thank you for a response though, maybe I missed something in the read...

KansasCityREPU

iTrader: (9)

The 79 flywheel will not work with the 85 motor. The issue is that the internal rotating assemble is balanced to the flywheel. The best bet is to use the 85 engine as is with the 85 flywheel. You can add the external bit like the water pump housing/pump from the 79 if you wish. I's just use the 85 stuff though. As far as the clutch/pressure plate and throw-out bearing, I'd get a new one because it cheap (Price: $129.99 from AutoZone Part Number: NU31084). If you don't want to spend any money, you can use the 79 215mm clutch disc on the 85 flywheel.

Jeff20B

iTrader: (13)

What you have is not actually a 79 flywheel. What I see in your pics is an 81-82 flywheel which works fine on a 79 engine.

The reason they did this is because they wanted to use the lightest stock flywheel you can get on any 76-82 12A. But, and it's a big but, it is not compatible with any 83-85 12A due to the rotors became lighter and require a different amount of "imbalance" to offset the lighter rotors.

Does that make sense?

Show us more pictures so I can pinpoint what parts you have.

As for your clutch, yep you can use the 215mm disc but not the pressure plate. You will need to get a correct 225mm pressure plate that fits 83-88. Might as well get a new disc. Don't bother changing the pilot bearing unless it's dead. But do swap in a new pliot seal. No clutch kits include them for some reason.