External 12a differences?
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Joined: Apr 2004
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From: South Jordan UT
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?
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?
Joined: Mar 2001
Posts: 31,833
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From: https://www2.mazda.com/en/100th/
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...
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...
Thread Starter
Senior Member
Joined: Apr 2004
Posts: 453
Likes: 0
From: South Jordan UT
j9fd, thanks for the info, I'll go look see what I've got.
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...
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...
damn! what kinda job do u have? i think i would've bought another rx3 and put the rest in the bank.
Joined: Mar 2001
Posts: 31,833
Likes: 3,232
From: https://www2.mazda.com/en/100th/
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....
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