possible to determine engine year without vin?
 

Hi,

I have a 12a (but not the rest of the car), and I'm trying to determine the year. I did find some info by searching:

"if it is from a gsl-se it would have motor munts on the front cover and none on the oil pan. If it is s4 it has motor mounts on the bottom of the engine. S4 rear iron inspection cover has 2 bolt holes one on each side, s5 only has 1 bolt hole on the inspection cover. thats the external differences. "

Trouble is, front cover could have been changed. There is a number on the engine - Z430000 and on each rotor housing - RD97 and CF533. I've been to the local mazda dealership, they couldn't help me. Do these numbers mean anything to anyone???

Thanks,

James

If its a 12a then its certainly not from a GSL-SE or a 2nd gen. Other than that, the engines are reletively generic. 13b's are easier to tell apart than 12a's IMO.

There are a few minor differences in 12A engines over the years. Exhaust ports are different on the 1980 and older, vs the 81-85. The rotor housings are also slightly different where the plugs go. The rear iron has a couple unique differences as well. Flywheels also vary for different years.
The bad news is, they can all be mixed and matched, so long as the internals and flywheel are kept as a matching set. This makes trying ID an engine even more difficult.

With the #s stamped on your housings, that's usually an indication of a rebuild. Post pics of your engine, lots of them. We will need to see pics of the carb, the spark plug holes, the front cover, the rear iron, both sides of the flywheel if it's off, is the dizzy electronic or points style and the exhaust ports, diameter of clutch disc (215 or 225 mm), yada yada yada.

Btw, post pics of your Opel. I've always thought the GT would a perfect candidate for a rotary swap.

Has it got any of the original rubber emission or fuel hoses on it?

They are all date coded from manufacture.

Hi,

Thanks for all the replies!!!

I'm sure the flywheel has been swapped, it is an 81-82, 215 mm clutch (apparently these were the lightest factory flywheel?) Got that mess sorted out when I ordered the clutch!
The carb is a Nikki 4 bbl, probably not the original. I'll have a look around for vacuum hoses, I think I still have the "rat's nest" somewhere. The distributor is not points, but again likely swapped, as I noticed the paint on it was different than other parts.
The exhaust ports!! That's a good clue, I'll get some newer/better pictures when I can (car is out to the paint shop at the moment). It is exhaust which started this whole quest to find the year - when I look for exhaust for a streetport on mazdatrix or racing beat, they vary by year. I already have the header, so maybe the year doesn't matter!!?? Can a 12A streetport be happy with one presilencer, or does it want two?

trochoid, thanks for your interest. Here's a picture, but the next time I see the car, it will be red.

cheers,

James

Well, since you have the header on it, you can just get the rest of the exhaust custom made. That solves the problem of finding the "correct" system, that will likely need to be modified to fit.
As for the exhaust ports. Do you remember if it has a pair or smaller ports just below (and towards the middle) of the larger ones? The RB header gasket *usually* has these small holes, as well. If the small ports are present, then the housings are 80 or older. If they are not present, 81-85.
As for the presilencer(s) debate, SP engines can be rather noisey. The more silencers you use, the tamer the sound level is.
Nice looking car, BTW.

Sweet!!! I've always liked the GTs. Be sure to post a full set of pics once it comes back from paint. Those wheels wouldn't be Voxx Ergs, would they? If they are, I have the same wheels on my 2nd gen.

As far as the carb, it doesn't appear to have the altitude compensator, so it's at least a pre-84. I've forgotten what year that item was added. In my sig line is a link to the online FSMs and factory carb manual which covers all of the 1st gen carbs. You might be able to determine what years your carb is and narrow down the engine year.

I don't recall if the GTs had single or dual exhaust. If it has dual, you could run a true dual system with a pre-silencer on each pipe. Just depends on how quiet you want the exhaust note and your budget. Another option is to run duals, with a pre-silencer on each, then collect the 2 just before the pipe goes over the axle.

Btw, what does a GT weigh in stock form and what was the origial hp?

If your taking off the exhaust make sure and take a picture of the exhaust ports. That's how they figured out what year my housings were.

-nick-

hey trochoid the gt has a single and if i remember 110 hp but not sure how much it weighs..have you seen one with a rotary engine though?? im interested..

In person, no I haven't. Did see a very rough one parked in someones yard with a V8 swap a few years back. It was a shame to see how chopped up the car was. A rotary would be an ideal swap for a GT though.

I've had my eye on early-mid 70's MG nearby for a rotary swap. But alas, too many other projects and not enough time or money.

:) i blame you now for putting ideas in my head!!! lol...i got this opal gt car show condition in my brothers garage very clean my stepdad had the engine taken out to get cleaned and he left and hasnt been back in 2 years,but its so purty i dont know but will post pics of it if you want when i can...forget time MONEYS the real problem lol

Cool! I will definitely check the exhaust ports when I get the car back.

Yeah, I've always liked the GT. I was lucky to find a rust-free one, but it didn't run when I got it, due to the fact the engine and transmission were missing. The rotary seemed a good idea. '71 GT curb weight, 2068 lbs, and a pathetic 83 hp.

The wheels I bought used, they were off a Honda, I believe they are Australian, and weren't very expensive.

There have been a few other swaps of rotaries into GTs, I've seen pictures, and TONS of V8 and V6 swaps. (I didn't want to do that.)

cheers,

James

A well tuned, street ported 12A, in a under 2100lb car. Gonna be a BLAST to drive.
Please post up some pics when you get it back.

Well James, you're making a good chice with the rotary swap. With the curb weight and a 200 hp street ported 13B 4-port, you would have the 3rd gen guys starting to worry. By then it would be time for a full brake, suspension and rear diff upgrade. Btw, once you start, it never ends, lol.

Keep us updated on your progress.

Sweet ride. A guy down the road from me has a couple sitting in his yard wasting away. A shame really.

Oh, man! you don't think I'd put a rotary in with the stock Opel suspension and brakes!!? Scary! I'm much too paranoid for that.
Front suspension is coil overs (original was transverse leaf), front brakes are rx7 gsl-se. Rear end is an IRS unit out of a BMW 325, now also coil-overs.

There is a guy here at my work trying to sell me a 13B with an intercooled turbo... perhaps in the future. I've seen lots of threads on swapping in the 13B in place of the 12a, should fit, I think.

thanks for your interest,

James

Nice upgrades, it ought to handle well, and stop unlike any other GT.
That 13B turbo would make it really give the stockish FD's a run for the money. Even with the street ported 12A, it should move along rather well.