12a mystery intake what to do?
 

Hi All,

I just picked up this mystery intake for $75 USD shipped. Can anyone tell me anything about it? I'm told it comes from an Rx3. I want to replace the stock intake on my 85 GS for one that flows better. This came with a plastic spacer from an 81 that fits. Can I just cut channels into the spacer or do I have to butcher my "new" intake? I have the oring coolant leak so I want to fix my car and pick up a few ponies at the same time. I also got a never used pacesetter header for $125 USD shipped.


https://cimg3.ibsrv.net/gimg/www.rx7...a76aab4d2e.jpg12a intake no shutter, smaller acv exhaust port. Whats the solenoid on the left do?
https://cimg4.ibsrv.net/gimg/www.rx7...f0bd4d87e5.jpgWhat does all this stuff do? I assume the brake booster vacuum source is the S on the right. What about the rest it. Whats the plastic tube in the middle?
https://cimg3.ibsrv.net/gimg/www.rx7...35dbe5a4d1.jpgrubber coating is ok but starting to peel in the middle.

It appears to be an RX-2 or RX-3. Perhaps 73 or 74 vintage. Transitioning from twin dizzy to single dizzy.

Yes on the S, and the plastic thing is what they called the altitude compensator but it can be used sort of as a PCV valve to keep your oil filler clear of condensation.

The gasket on top of the mani can be removed as the one on the modern spacer works fine as long as it is still there.

Yes you will need to butcher your "new" mani to get channels. Think of it like this. The Nikki prefers channels. I have two of these old schools (early and late style) that were already butchered by the PO's hogging out of the runners which kills velocity, but they did not cut any channels. Ugh. So that's what I get to do.

FWIW, the intake where I got 32mpg didn't have channels, I'd blocked them off.

Do twin dizzy and single dizzy intake manifolds have the same bolt pattern to the engine? I may have just bought a twin dizzy 12A.

Hey Peejay, how was the power on your intake with blocked channels (any difference positive or negative)? I understand these early ones make better power. I'm reluctant to just start cutting away since it will be hard to replace and I have no idea what I'm doing. :)

I don't know how realistic it is but I'm hoping to find about 20 hp with a better intake and the cheap header... poor man's fully mechanical gsl-se.

When I bought it, the bolt patterns seemed the same. The ACV port for the exhaust is a little smaller. BTW, what does the dizzy have to do with the intake?

The engines were otherwise completely different, so I am led to believe. Very little interchanges between a twin distributor and single distributor 12A. Infact the changes are so significant that Mazda was internally calling the new engine "12B".

Power wise, it wasn't stellar but the off idle drivability was incredibly crisp.

Yup thats junk. You'll just have to ship it to me do.I can properly dispose of it...

your right, I should have just bought an automatic miata

yes. the irons and housings are pretty radically different 68-73 and 74-85, most of the rest of the engine was revised, but things like the oil pump and e shaft are compatible.

so if you wanted to build a twin dizzy engine, because its cool, you would want some 3mm seal rotors, because you can actually buy those. the chrome on the housings requires a carbon seal, but you can actually buy those. any 12A intake works. exhaust bolt pattern is different, but nothing you can't fix with a drill.

port it to 74, or 110 cosmo specs, and its about ~130hp, in the right car, like a Lancia Scorpion, it would be fun

The 6 spd dct in the new mx5 is actually boss.

Not sure where that came from tho

I have tons of twin dizzy engine stuff if anyone is interested. I have rotor housing galore along with irons, rotors, front covers, etc. Even a complete engine and trans still together with compression.

Im sure its fun I just prefer manual. I sell cars and get to drive a lot of different stuff. Auto doesn't do it for me - too much like a video game.

I was close to picking up a NA 1.6 stick Miata off kijiji for $2500CDN ($2000 USD) in very good shape... but someone beat to it by 10 minutes. Looking back, I'm very glad I bought an FB rx7 instead. I just need to figure out what to do with the intake and how 😀

Well i guess I'm fucked. Looks like the RX-3 is getting a 13B.

You can? So I bought two truckloads (well, trailer-loads, I refuse to drive trucks) of 12As last winter for nothing? (spoiler alert: NONE of them had good rotors. All garbage.)

You can? Racing Beat and Atkins say 12A 3mm carbons NLA.

i checked, and Mazda has them still. 4352-11-301.