Mazdax605

iTrader: (5)

Hey guys,

Well today I traded a fellow rotorhead my old 85 12A that was in my 83 LE for many years for an unknown 12A that he got with an old RX-3 race car.

It came out of an automatic car as far as I can tell with it having a removable counterweight on the rear,but no flywheel or flex plate. It appears to be an earlier engine as it doesn't have a oil pressure sender,but it does have spot where you can remove an allen head plug,and thread one in like on my 78 production GS. It has a single distributor that is points type. I did see R5 cast into the centre plate near the oil fill neck if that helps identify it.

My guess is another 79-80 RX-7 12A or maybe a RX-3 12A from a later vintage one.

Any help would be appreciated.

trochoid

iTrader: (6)

Jeff20B is your answer man for this one. Pics would help a lot too.

Mazdax605

iTrader: (5)

I knew you would ask for pics. They are crappy as my camera isn't the greatest,and it is very dark in my van,but you get the idea. The more I think of it the more I think it is a 76-78 RX-3 engine with the tall centre ports and 16 tension bolts. The unfortunate part of that is I don't believe they are nitrided. Jeff can help me out I am sure.

On with the dam pics you say? Here you go:

http://web.me.com/cdirado/Diradosite/RX-7-parts_.html

Chris

mazdaverx713b

iTrader: (91)

any chance it could be an engine from a 79? the points style distributor, the front engine mount, the newer style mazda script on the rotor housings, and the omp lines make me think SA engine.. the odd plate/shim on the rear iron is strange. good question on what year is from. any engine number stamped into it?

Mazdax605

iTrader: (5)

Bump. Hey Jeff any chance you can help? I am 99% sure it is a 78-80 RX-7 engine,but the centre ports are throwing me off,so maybe a late RX-3 engine.

Mazdax605

iTrader: (5)

bump

rxtasy3

iTrader: (2)

i too will go with 79-80. the earlier had a sensor in the top of the center housing. at least my 74 13b did.

j9fd3s

iTrader: (3)

it looks factory.. edit, black paint on the tension bolt heads? hmmmm

nitrided side housings make it 79+

its also sporting an rx7 oil pan, rx3 is the other way around.

the distributor should have a number on it, like 8871

in reality, mazda superceeded the 76-78 rx3 parts to the rx7 spec, so if you were buying new when they were available, the 76-80 engines were made the same.

the rx3 engine will differ by having non nitrided side housings, painted black.

Mazdax605

iTrader: (5)

Thanks guys. I had no idea the RX-3 oil pan was different. Clearence issue with the cross member being different on the -3?

I have a feeling this engine has been apart,but I am not sure. The Mazda casting on the housings has been painted yellow as well,but that means nothing. The freeze plugs in the rear plate look like they have been replaced,but I don't think Mazda,or any other rebuilder would go to this trouble when rebuilding an engine,so maybe they just rotted out,or did thier job at some point in the life of the engine.

I will check the distributor later. I will also look for a part number somewhere on the engine. Where should it be?

Chris

Jeff20B

iTrader: (13)

Rear plate looks like a nitrided R5, 18 tension bolts (you forgot the two lower ones). Intermediate also looks nitrided. Front plate may be from a '76-'78 because it looks a little rusty. Probably been rebuilt becasue freeze plugs look aftermarket. Good thing your rear plate has a little plug in the oil prerssure hole. Nitrided R5 rear plates aren't threaded there. Either somebody rebuilt the engine and added the threaded hole, or it's an early non nitrided plate that looks nitrided in your pictures. Notice it looks gray? It doesn't look painted black.

Housings look like somebody filled some thermal reactor holes with devcon or quicksteel. Please confirm whether they're just dirty or actually filled.

Mazdax605

iTrader: (5)

Those holes are filled,and they look like they are a pair of fronts,as the holes are both pointing rearward.

I caught the freeze plugs as well.

So Jeff,are you thinking a mix of parts,but mostly a 78-80 RX-7 engine?

Jeff20B

iTrader: (13)

Yes, a mix of parts. Do you know how to measure the rear counterweight to tell what year rotors you've got? Mazdatrix explains where to measure it. I'd say you most likely have the big half circle '76-'80 front counterweight.

Mazdax605

iTrader: (5)

I will have to take the front cover off. I can tell you I have a rear counterweight from when I had the lightweight steel flywheel on my 78 production RX-7,and it is exactly the same as the one on this engine aside from it has a few different holes drilled in it for balance.

So as long as everything is in usable condition then I have a good core engine,correct?

Jeff20B

iTrader: (13)

You're the one tearing it down. You tell me.

Mazdax605

iTrader: (5)

I guess I worded this wrong. If it is all in usable shape is it okay to use a mix of parts like this?

Jeff20B

iTrader: (13)

Someone before you did, and the engine ran. I do this type of thing all the time.

Mazdax605

iTrader: (5)

Are the centre ports abnormally large,or am I confused? Maybe someone ported it some?