Calling old school gurus... what the heck 12A did I just get?
12-28-16, 04:36 PM
#1
Old [Sch|F]ool
Thread Starter
Calling old school gurus... what the heck 12A did I just get?
Just got home from picking up a mystery 12A. Didn't have time to take photos because my fingers were numb and I had to pee, and two things my garage doesn't have are heat and running water. So I got it off the trailer and put everything away and got my cold self home.
The engine had an EGR valve, which gut instinct told me was an '80 California model. However there's other weirdities with the engine. It had a flywheel nut lock plate, something I've never seen before even on a friend's '79 engine. (There was also a dowel to hold the plate in place) Very heavy 215mm flywheel.
The engine has a REAR sump oil pan. It doesn't appear to be a stock pan turned around, the curves in the front and the rear seem tp match. Drain plugs on both sides. Very curious.
The exhaust port inserts are "contoured", as if to direct the airflow coming in through the air injection. My '80 engine did NOT have inserts like this!
The really weird thing is the distributor. It is a HALL EFFECT distributor! It has a bizarre looking cap and rotor assembly, too, like the contacts are axial instead of radial. I thought Mazda went straight from points to VR sensors. I know the distributor from my '80 was identical to an '81-85 except for wiring coming out the side instead of having the ignitors bolted directly to the housing. Very very strange! Sadly it looks like it's been exposed to the elements a lot so it is probably NFG.
Pictures to come probably tomorrow. Any other things I should look for to help ID the engine? I don't know anything about side housing casting numbers, so I don't even know what to look for there.
The engine had an EGR valve, which gut instinct told me was an '80 California model. However there's other weirdities with the engine. It had a flywheel nut lock plate, something I've never seen before even on a friend's '79 engine. (There was also a dowel to hold the plate in place) Very heavy 215mm flywheel.
The engine has a REAR sump oil pan. It doesn't appear to be a stock pan turned around, the curves in the front and the rear seem tp match. Drain plugs on both sides. Very curious.
The exhaust port inserts are "contoured", as if to direct the airflow coming in through the air injection. My '80 engine did NOT have inserts like this!
The really weird thing is the distributor. It is a HALL EFFECT distributor! It has a bizarre looking cap and rotor assembly, too, like the contacts are axial instead of radial. I thought Mazda went straight from points to VR sensors. I know the distributor from my '80 was identical to an '81-85 except for wiring coming out the side instead of having the ignitors bolted directly to the housing. Very very strange! Sadly it looks like it's been exposed to the elements a lot so it is probably NFG.
Pictures to come probably tomorrow. Any other things I should look for to help ID the engine? I don't know anything about side housing casting numbers, so I don't even know what to look for there.
Last edited by peejay; 12-28-16 at 04:49 PM.
12-29-16, 01:58 PM
#6
carb whisperer
I posted here years ago about an oddball distributor I found on an '81 12a in a junkyard (build date was early 81) and everybody called it a hacked up distributor. I actually kept it, and have it in storage. It's NOT points, and it DOESN'T have ignitors.
I'll dig it up this weekend, maybe it's the same as yours? Does it have TWO black/white stripe wires on it instead of one like normal?
I'll dig it up this weekend, maybe it's the same as yours? Does it have TWO black/white stripe wires on it instead of one like normal?
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12-29-16, 07:06 PM
#8
Old [Sch|F]ool
Thread Starter
That helps a bit actually 
I too was hoping Jeff would chime in. He seems to have the Knowledge regarding which housings went to what engines.
Many photos to follow.
First the distributor. I was wrong about the cap, it was dark out when I looked at it. It is just a pre-80 points cap so I took no photos.
Hall effect sensors and shutter wheel? In MY rotary distributor? It's more likely than you think!
I too was hoping Jeff would chime in. He seems to have the Knowledge regarding which housings went to what engines.
Many photos to follow.
First the distributor. I was wrong about the cap, it was dark out when I looked at it. It is just a pre-80 points cap so I took no photos.
Hall effect sensors and shutter wheel? In MY rotary distributor? It's more likely than you think!
12-29-16, 07:08 PM
#9
Yep, someone like me may have seen a 12A like this before... and then maybe not.
I have seen many flywheel nut locking plates and roll pins on 70s stuff. Have not seen a hall effect dizzy yet though. My 6 port 12A middle iron does have an EGR port, and motormount studs like a GSL-SE. Does yours have studs?
I'm betting it has X castings. Probably does not have T castings. Heck it might have a variation of R5...
Yes, be prepared for a 30 pound 215mm flywheel.
Look in the pilot seal hole. Make sure it has a blind plug. If not, look to the lower right corner of the rear iron for an oil return line; you might have an auto-stick engine on your cold garage floor.
What do the intake ports look like? Tall runner or short runner on the middle iron?
I'm guessing the rotor housings have the weird ring-sleeves and a tube angled to capture some exhaust and pipe it into the ACV channel within the middle iron, or it puts air pump air into the exhaust ports. Kind of an early way to get air to a catalytic convertor. I'll dig up a pic:
I have seen many flywheel nut locking plates and roll pins on 70s stuff. Have not seen a hall effect dizzy yet though. My 6 port 12A middle iron does have an EGR port, and motormount studs like a GSL-SE. Does yours have studs?
I'm betting it has X castings. Probably does not have T castings. Heck it might have a variation of R5...
Yes, be prepared for a 30 pound 215mm flywheel.
Look in the pilot seal hole. Make sure it has a blind plug. If not, look to the lower right corner of the rear iron for an oil return line; you might have an auto-stick engine on your cold garage floor.
What do the intake ports look like? Tall runner or short runner on the middle iron?
I'm guessing the rotor housings have the weird ring-sleeves and a tube angled to capture some exhaust and pipe it into the ACV channel within the middle iron, or it puts air pump air into the exhaust ports. Kind of an early way to get air to a catalytic convertor. I'll dig up a pic:
Last edited by Jeff20B; 12-29-16 at 07:11 PM.
12-29-16, 07:16 PM
#11
Old [Sch|F]ool
Thread Starter
Engine housing photos. Ignore the goofy plumbing mods, this engine used to be in a Spitfire or Midget or something. Plug side:
Notice the strange boss below the water outlet, which appears to be threaded. Also notice that there is a tapped (and plugged) hole for an oil pressure sender. '80 RX-7s did not have oil pressure gauges or idiot lights, just an oil level idiot light. Rotor housings are flat faced around the plugs.
R5 rear end housing. Odd looking tension bolts, they are completely flat.
NO intermediate housing. Also notice the funky oil filter pedestal adaptor, it's not a homebrew setup, it has a part number cast into it! Rag is covering some pipe, pipe elbows, and short lengths of cut-off -8 braided hose, which make a dandy carrying handle but are really sharp, thus the rag.
Top of engine, clearly this is RX-7 era script on the rotor housings and not the early style.
R5 front end housing as well.
Funky, funky exhaust port sleeves!
I kind of forgot to get pictures of the oil pan.
Notice the strange boss below the water outlet, which appears to be threaded. Also notice that there is a tapped (and plugged) hole for an oil pressure sender. '80 RX-7s did not have oil pressure gauges or idiot lights, just an oil level idiot light. Rotor housings are flat faced around the plugs.
R5 rear end housing. Odd looking tension bolts, they are completely flat.
NO intermediate housing. Also notice the funky oil filter pedestal adaptor, it's not a homebrew setup, it has a part number cast into it! Rag is covering some pipe, pipe elbows, and short lengths of cut-off -8 braided hose, which make a dandy carrying handle but are really sharp, thus the rag.
Top of engine, clearly this is RX-7 era script on the rotor housings and not the early style.
R5 front end housing as well.
Funky, funky exhaust port sleeves!
I kind of forgot to get pictures of the oil pan.
12-29-16, 07:34 PM
#12
Old [Sch|F]ool
Thread Starter
Finally, the flywheel.
Looks like the Mazdatrix photo of a '79-80 12A unit, but they say there's no number cast in the engine side, this one clearly has a 3 cast in place.
Looks like the Mazdatrix photo of a '79-80 12A unit, but they say there's no number cast in the engine side, this one clearly has a 3 cast in place.
12-29-16, 07:38 PM
#13
Ok I know what you have.
You have a J-spec 18 tension bolt R5 and NO 12A with the rotor housings that have dual-wall sleeves. I've seen a couple of these, both 12A and 13B versions. Even Ray Green has a set of housings with these which I tried to explain how to cut out the inner sleeve for a better flowing (And turbo-capable) outer sleeve, he just didn't understand. I can dig up the thread later with pics and info.
The R5 end irons might not be nitrided but the intermediate plate is nitrided. They came from the factory like this! The tension bolts are factory as well.
The oil filter pedestal is simply a tall style that they chopped to relocate the oil filter. They also welded or brazed an extension to the heater core nipple fitting.
The oil pan is a factory one they flipped around and redrilled some of the holes. The pickup tube has been extended.
Nothing off the wall or strange about this engine at all. Count on using any 79-82 rear counterweight and be prepared to see a half circle front CW which can be swapped out for a slightly light 81-82 style if desired.
Now, the thing that is weirding ME out about your engine is the odd looking pattern on the intake gasket. Judging by their OMP rod and what looks lie a spring down next to the front cover, the carb they used wasn't stock. What kind of ugly intake manifold did they use? It clearly has a bad lip promoting the effects of reversion. Yuck. I bet they were losing power and not even knowing it. But then again, 70HP in one of these cars feels fast... so who knows.
You have a J-spec 18 tension bolt R5 and NO 12A with the rotor housings that have dual-wall sleeves. I've seen a couple of these, both 12A and 13B versions. Even Ray Green has a set of housings with these which I tried to explain how to cut out the inner sleeve for a better flowing (And turbo-capable) outer sleeve, he just didn't understand. I can dig up the thread later with pics and info.
The R5 end irons might not be nitrided but the intermediate plate is nitrided. They came from the factory like this! The tension bolts are factory as well.
The oil filter pedestal is simply a tall style that they chopped to relocate the oil filter. They also welded or brazed an extension to the heater core nipple fitting.
The oil pan is a factory one they flipped around and redrilled some of the holes. The pickup tube has been extended.
Nothing off the wall or strange about this engine at all. Count on using any 79-82 rear counterweight and be prepared to see a half circle front CW which can be swapped out for a slightly light 81-82 style if desired.
Now, the thing that is weirding ME out about your engine is the odd looking pattern on the intake gasket. Judging by their OMP rod and what looks lie a spring down next to the front cover, the carb they used wasn't stock. What kind of ugly intake manifold did they use? It clearly has a bad lip promoting the effects of reversion. Yuck. I bet they were losing power and not even knowing it. But then again, 70HP in one of these cars feels fast... so who knows.
12-29-16, 07:38 PM
#14
Your flywheel is a basic 30 pound 76-80 215mm flywheel. What a horrible choice in such a small light car. 
I've driven my rotary powered MG Midget one time with a 30 pound flywheel and it was pretty stupid. Went light steel and it was lightyears better. I might go even lighter than that next.
I've driven my rotary powered MG Midget one time with a 30 pound flywheel and it was pretty stupid. Went light steel and it was lightyears better. I might go even lighter than that next.
Last edited by Jeff20B; 12-29-16 at 07:41 PM.
12-29-16, 07:49 PM
#16
Old [Sch|F]ool
Thread Starter
Well, this engine came from the same guy I bought a Dell'Orto 48DHLA from a couple years ago. And two 6-port engines. And a rotary-to-Midget header (looks neat, it curls under the engine) that he fabbed. And a early bellhousing, Kennedy adaptor, and Ford T5. And a bunch of other misc. stuff...
So who knows what it had?
So who knows what it had?
12-29-16, 07:52 PM
#17
Your R5 irons are likely not nitrided. How do I know this? Because I can clearly see a blocked off threaded oil pressure hole.
It seems Mazda stopped drilling and threading a hole there on their later nitrided R5 engines which had stupid full flow oil squirters in the shaft. I think they were embarrassed to let people know how low the idle oil pressure is on those engines. Like 10psi. That's just unnecessary to run them on the street.
Anyway, your shaft should possess the checkballs so nothing to worry about. But just to be on the safe side, look at the color of the screw cap head. If dark, it is full flow and should be swapped out. If lighter colored like yellow cadmium plating, then it is a checkball type. You can poke a toothpick or something gentle into the hole to see how deep it goes. Cross reference with a shaft from a 7.
It seems Mazda stopped drilling and threading a hole there on their later nitrided R5 engines which had stupid full flow oil squirters in the shaft. I think they were embarrassed to let people know how low the idle oil pressure is on those engines. Like 10psi. That's just unnecessary to run them on the street.
Anyway, your shaft should possess the checkballs so nothing to worry about. But just to be on the safe side, look at the color of the screw cap head. If dark, it is full flow and should be swapped out. If lighter colored like yellow cadmium plating, then it is a checkball type. You can poke a toothpick or something gentle into the hole to see how deep it goes. Cross reference with a shaft from a 7.
12-29-16, 07:56 PM
#18
Old [Sch|F]ool
Thread Starter
To be honest this engine was an aquisition of opportunity. I have a hurt 12A in my new car and I'm in acquire stuff first, ask questions later kind of mindset.
I'm leaving in a few hours for Alabama, to pick up some more engines and other stuff
Basically the rest of the stuff that came with the car, like the louvers that are currently not on the car, things like that. Oktavia is going to be stuffed to the gills and the trailer's gonna be bottomed out!
I'm leaving in a few hours for Alabama, to pick up some more engines and other stuff
Basically the rest of the stuff that came with the car, like the louvers that are currently not on the car, things like that. Oktavia is going to be stuffed to the gills and the trailer's gonna be bottomed out!
12-29-16, 08:17 PM
#20
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Either Nanase or Kyouko. Haven't decided. Nanase is the perfect name for any RX-7, really, but Kyouko is also a redhead, and, well, there's kind of a theme going on what with Oktavia and all...
12-29-16, 09:18 PM
#21
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nice find, i would date that engine to about 78-79, its got the white pulleys, and it has the casting for the Mazda automobiles, but no automobiles.
Mazda put rotaries into everything in 78, and everything used a different oil pan than the Rx7, so it may be something like that.
i forget how we know this, but they did have some odd setups with like bigger flywheels, and hotter thermostats and EGR and stuff
Mazda put rotaries into everything in 78, and everything used a different oil pan than the Rx7, so it may be something like that.
i forget how we know this, but they did have some odd setups with like bigger flywheels, and hotter thermostats and EGR and stuff
12-29-16, 10:31 PM
#23
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Thread Starter
That would be difficult to do with no water pump housing
I don't think the oil pan was rotated. It didn't look redrilled, and the curvature at the front matched the front and vice-versa. The front cover is shaped differently from the rear end housing. I recall that the left side had two plugs, like for the oil temp switch and oil level switch, those would be on the right side if the pan was simply flipped around.
I don't think the oil pan was rotated. It didn't look redrilled, and the curvature at the front matched the front and vice-versa. The front cover is shaped differently from the rear end housing. I recall that the left side had two plugs, like for the oil temp switch and oil level switch, those would be on the right side if the pan was simply flipped around.
Last edited by peejay; 12-29-16 at 10:33 PM.
12-31-16, 06:48 AM
#25
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Thread Starter
Someone down the chain of ownership from the swapper to me knew where it came from. The front mount plate is massively modified, it extends waaaay out and up. I've never seen a Spitfire before, but I have seen Midgets (and I rebuilt the overdrive unit in one, which requires removing the engine and trans assembly for chunderheaded English reasons) and this mount doesn't look like it'd be Midget-friendly, but another mount plate I got from my previous parts haul did some with a modified plate that looked like it'd bolt up to a Midget chassis. So I am thinking that this one was in a Spitfire, maybe.
I'll ask if I can get to sleep. Picked up two more core engines. These ones are boring common American-market FB engines, nothing at all fancy Also the world's largest supply of 24 spline axles and a couple sets of Tokicos and a full set of Bilstein HDs if you can believe that. I passed on a whole shitload of Blues and some Konis, at some point it's no longer getting parts you think you need and just becomes hoarding for the sake of hoarding, and I want to avoid that.
I can easily justify getting all the 12A things I can get my hands on, though
I'll ask if I can get to sleep. Picked up two more core engines. These ones are boring common American-market FB engines, nothing at all fancy
Also the world's largest supply of 24 spline axles and a couple sets of Tokicos and a full set of Bilstein HDs if you can believe that. I passed on a whole shitload of Blues and some Konis, at some point it's no longer getting parts you think you need and just becomes hoarding for the sake of hoarding, and I want to avoid that.I can easily justify getting all the 12A things I can get my hands on, though