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-   -   External 12a differences? (https://www.rx7club.com/1st-generation-specific-1979-1985-18/external-12a-differences-862934/)

clubber 09-13-09 06:27 PM

External 12a differences?
 
Guys, I have a non RX-7 chassis with a 12A engine (maxton rollerskate). Is there any way to tell if it's series 1,2, or3 externally? I know it has an electronic dist but would like to know which flywheel counterweight to get on a light flywheel. Are there any easily identified extrtnal clues?

rxtasy3 09-13-09 07:18 PM

u should be good with anything from 81 to 85. i remember seeing a build up many yrs back on one of those that motorweek mag did using the engine from 83 or 84. to this day i still wish i could get my hands on one. how'd u come across the one u got?

j9fd3s 09-13-09 07:57 PM

yes there are.... but only if its STOCK, all the parts interchange so its possible to have a mutt...

early 78-79, off white pulleys for the w/p and crank. rotor housings have ribs going front to back.

79-80 pulleys will turn black at some point, the 80 california engines have an egr valve on top of hte center housing.

81-82. they switched to cats, so the rotor housings are also different, they are smooth on top with an "H" shaped thing on top. there is also a rectangular port under the center intake ports. flywheel is also lighter, but is compatible with the earlier rotors.

83-85. they went from the air/liquid oil cooler to the "beehive" style. the rear heater hose outlet becomes a "T". the 83-85 rotors are lighter, they are stamped NF and NR in the combustion recesses.

the pre rx7 engines, should have black painted irons, 74-75 have the big font type on em (and more port timing too!) 76-78 have small font "mazda automobiles" stamp

in japan they had a 12a turbo, and a 6 port 12a engine, the 6 port intake is RARE...

clubber 09-13-09 08:18 PM


Originally Posted by rxtasy3 (Post 9493135)
u should be good with anything from 81 to 85. i remember seeing a build up many yrs back on one of those that motorweek mag did using the engine from 83 or 84. to this day i still wish i could get my hands on one. how'd u come across the one u got?

I got mine from wirewheel.com. They are in florida and if you look on their website, they have another. The one they have now has a 13B and a top, mine didn't have a top. It's the same as I paid too.

j9fd, thanks for the info, I'll go look see what I've got.

80's old school 09-13-09 09:25 PM


Originally Posted by j9fd3s (Post 9493231)
yes there are.... but only if its STOCK, all the parts interchange so its possible to have a mutt...

early 78-79, off white pulleys for the w/p and crank. rotor housings have ribs going front to back.

79-80 pulleys will turn black at some point, the 80 california engines have an egr valve on top of hte center housing.

81-82. they switched to cats, so the rotor housings are also different, they are smooth on top with an "H" shaped thing on top. there is also a rectangular port under the center intake ports. flywheel is also lighter, but is compatible with the earlier rotors.

83-85. they went from the air/liquid oil cooler to the "beehive" style. the rear heater hose outlet becomes a "T". the 83-85 rotors are lighter, they are stamped NF and NR in the combustion recesses.

the pre rx7 engines, should have black painted irons, 74-75 have the big font type on em (and more port timing too!) 76-78 have small font "mazda automobiles" stamp

in japan they had a 12a turbo, and a 6 port 12a engine, the 6 port intake is RARE...

Cool... the 12a in my 84 autocross car has "Mazda automobiles" stamped on the front housing...never knew what that was off of. Figured the PO rebuilt the engine and must have used an earlier housing. I know it is NOT an older engine because the center irons have the rectangular slotted hole under the two intake ports....

rxtasy3 09-13-09 11:21 PM


Originally Posted by clubber (Post 9493269)
I got mine from wirewheel.com. They are in florida and if you look on their website, they have another. The one they have now has a 13B and a top, mine didn't have a top. It's the same as I paid too.

damn! what kinda job do u have? i think i would've bought another rx3 and put the rest in the bank.

j9fd3s 09-14-09 11:16 AM


Originally Posted by 80's old school (Post 9493402)
Cool... the 12a in my 84 autocross car has "Mazda automobiles" stamped on the front housing...never knew what that was off of. Figured the PO rebuilt the engine and must have used an earlier housing. I know it is NOT an older engine because the center irons have the rectangular slotted hole under the two intake ports....

yeah everything interchanges, only real difference is the smog ports anyways


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