In my widebody, I know the PO dropped a new engine in it.

Unfortunately, the man who built it passed away and I was only able to talk to his wife about the car.

I have a feeling the engine is from an 81 or 82, but I am not 100%. I am slowly figuring out what he has done to this car, but I am still stuck on engine.

I know there were some huge differences, such as the dizzys. I have an electric distributor with 2 Mallory ignition modules going to it. 81 - 85 for the years of the electric dizzy, right?

Also, I have an oil cooler versus the beehive. I know the beehive was introduced in 84.

With those two things in mind, I think I have either an 81 or 82 engine.

What other determining factors are there on the 12a's to establish which year/series it's from?

I know there is something about an "H" on the housings for a certain year, differences with catalytic converters, weight of the rotors, flywheels, etc. Any help is great. Possibly an archive worthy thread in the making?

Thanks,
Chris

 

Start with posting pics of the top of the engine housings, the spark plug holes with plugs removed. The beehive came out in 83. There's a difference in the the egr porting and intake manis, along with the clutch diameters, depending on the years. The ignition mods can be done on any model year from 80 or earlier.
If you happen to have the tranny out, pull the flywheel and check it's part # against Mazdatrix's list.

Jeff20B will be your most likely best answer.

 

pics of the engine will get you the answer you seek a lot quicker. to add to the above, look at the left side of the engine on the rear iron. there is a coolant hose going to a metal pipe sticking out of the rear iron. if the pipe is "T" shaped then the engine (or at least rear iron) is from an 83-85. if not, then its an earlier engine. it is possible to swap that coolant hardline out so that is not a definate indicator. i can post a pic of a 12A from an 85 and one from an 81 if that will help you.

 

Eye brows over the spark plugs holes indicate an 81-85 12A.

Electric dizzy is stock on 80-85 12A. The 80 electric dizzy has the igniters on the
driver side shock tower.

We need pics of the top of the keg to go further I think. Also if you pull the cap on
the dizzy and the rotor and get a pick I can tell you which dizzy you have
regardless of where the igniters are or aren't.

 

If we could get enough people to post their engine serial numbers for engines of known build years, we could probably shotgun a good estimate just from examining the ranges of those numbers.

The engine serial number is under the alternator, stamped on top of the front iron.

The irons also have "series" numbers cast into them, but they're really only visible with the engine out and partly disassembled, so that's not much help.

 

Heres some of the pictures;

Dizzy:


H / I casting mark:


Front housing:


Rear Housing:


Few more questions

The sensor on the back of the waterpump, what is that for? I tried to search and couldnt really get a clear answer. Its this pic; HERE. I seem to recall someone from Atkins told me for cold start?

The temp gauge uses THIS sensor, right?

Also, I have tested my fuel sending unit, and it appears to be shot. It is reading OL for ohms, meaning most likely a winding of sorts is broken. The wiring all tests fine for continuity, and when I quickly shorted the gauge out to read 0 Ohms, the gauge worked perfect so I know thats not the problem. Where can I find a replacement? Will an aftermarket one from summit work to give me a decent reading, or what are the other options seeings how they are NLA.

Thanks!

 

Sensor on the back of the water pump: that's the water-temp sensor that runs the choke and the hot-start assist, IIRC.

On fuel sender; new ones are very pricey when you can find them, but junk-yard items can be had pretty cheap. SA & FB are different with regard to connections & length. I have a thread in the Archives that shows the innards and how they come apart. Sometimes you can fix them.

 

The one in the last picture runs the gauge, the one on the back of the water pump tells your choke when it's warm enough to kick off (and I believe is also hooked to that computer-esque thing in the passenger footwell)

Jon

 

'81 Y rear plate

 

right. screw in heater hose... which is rather nice. 8871 part number, its 79-81

rotor housings are the 84-85 style, the 81-83 dont have all the dimples in the casting by the spark plugs.

which means its rebuilt

 

Hot start assist uses the sensor in the oil pan. The one on the back of the water pump housing is for the choke only.

 

Looks like an oil fitting, so most likely an '81 Y plate. Or possibly could be a 79-80 R5 plate with a drilled and tapped hole.