I am looking at a parts car and its a 79 body with a rebuilt 12A ... owner can't confirm its a 79-80 12A as opposed to later model FB 12A swapped into it . Other things have been modded so can't tell for sure like a header and newer alternator. Air cleaner has built in Carbon cannister but carb was also rebuilt and may not be 79-80 carb either

Would like to know how to confirm the Keg is actually a 79-80 ??????? what would be a sure indicator ?

 

That's harder than it sounds, without taking things apart. most of the easy indications are covered.

FOMC, or Beehive oil cooler?

Wasnt there a tapped hole for the oil pressure sender on the 81+ motors, which is undrilled on the 80 and younger kegs?

The tension bolt count changed at one point , but you'll never spot it without removing the trans.

 

FMOC .... that could be the indicator its still a 79 .

where is the oil pressure sender unit ?

 

You know....unless I am forgetting...My 1984 12a says "Mazda automobiles" on the rotor housing. The 80' "I think" only says Mazda.

 

The 79-80 12As don't have the eyebrow over the plug holes right? You know the ones that force you to use a special thin wall socket to change the plugs.

 

Tru that Tim. As far as the irons go, no real way to tell without taking the engine apart. Whan I tore the engine down that was in my old SA, it had SA housings with FB irons. Unless you have owned it since new, it's hard telling.

 

If I recall correctly, the oil pressure sender was on the rear iron, driver's side, below the oil filter pedestal.

I know all the front irons bear a serial number stamped on top, about where the alternator goes, but I've never seen a reference that lists which engines went with which years, or which cars.

 

the 74-80 rotor housings have extra ribs in the castings.

like these, although this is an older engine http://www.rotaryresponse.com/RHousi...rall72auto.jpg

the irons are different, the casting is more square, but its subtle, and really except the oil pressure sender, they are functionally the same

early SA engines also have pulleys that are creme colored, later pulleys are black.

 

18 bolts on the 79/80
17 on 81/85

on the front cover, the timing mark is very thick on the 79/80 and very thin on the 81/85

no oil pressure sender on the 79/80 (screw in type on rear iron)

if the engine was rebuilt, it could have newer housings, so that doesnt fly

 

OK, this is a 1980 12a rear housing, driver side:
Arrow shows where the non-penetrating oil pressure sensor holes are:


The holes are in the casting, but they do NOT go thru to the oil journal. On 81-on engines, I believe, at least one is drilled thru and the oil pressure sensor goes in it.
(closeup, shot sideways.)


If somebody with a for-sure 81-later 12a could verify the sensor or get a pic of it, we'll have a pretty reliable way to detect early rear irons, without disassembly.

 

On the mazdatrix website there is a page w/photos explaining visual differences between the 79/80 Federal, 80Calif ERG equipped and 81-85 engines. Heres the address; http://www.mazdatrix.com/eng12aid.htm

 

I like the way Divin drew the arrows

 

Divin, here is a picture of the rear housing on my 84. Looks like a temp sensor on the left and oil pressure on the right.

Also note no "eyebrows" above the sparkplug.

 

I also like how messy his workbench is....Divin...you feeling OK????.....Fever maybe??

 

Also my 84 has "Mazda Automobiles" written on the pront rotor housing only....not the back.

I don't remember the "Automobiles" verbiage written on my 1980.

 

My workbench gets a thorough cleaning tonite, as I'm swapping between projects (the Z gets new struts this weekend). It's usually got three or four different things going on at any particular time.

Right now, it's got the following sections working:

Air cleaner base paint stripping
Steering gear cleanup and paint prep
350Z strut swap prep
Messy section that was just used for moonroof resto finished last week, which is where I parked that housing

Clean desk = messy mind, and all that.

 

Interesting, 80's: notice that the casting actually changed shape between your housing and mine; there's not as much of a 'boss' under the temp sensor area. Looks like it was angled to make more room for the pressure sensor.

And yes, the 80's rotor housings only said "MAZDA." The front housing was the first one that went NLA from Mazda, so perhaps your last build required that a later front housing be used.

 

thanks all ............ the thread help confirm its not a 79-80 12A.