BLACKrotor92

iTrader: (3)

help...wuts the diff. between a twin dizzy and a single 12a

Zemus386

twin...dizzy? no ******* clue what you mean.

As far as I know rx-7's only come with a single engine. You could hook two of the same together for a twin?

Im lost......

BLACKrotor92

iTrader: (3)

rx2s come with 2distributors and the 1st gens come with one

bluemunkey1820

Just how they did it back in the day. You can swap a first gen cover to go single or you just have to adjust leading and trailing timing independently.

Dom_C

I beleive that some first gens also came with the twin dizzy

Tom93R1

iTrader: (2)

If you arent concerned about originality the best bet is to ditch the twin dizzy and go with a 82-85 rx7 electronic ignition setup single dizzy.

I dont know what your question was about the difference between twin vs. single

jgrewe

iTrader: (1)

I'm just learning the old skool stuff but I think the twin dizzy 12A's had the 6mm apex seals.

I would add a question that maybe the OP is thinking of as well. Do the old twin dizzy's perform as well as a single newer dizzy? Or is it six one way, half dozen the other?

Jesuscookies

iTrader: (1)

Harder to get the timing right on the twin, and the older engine seals were for ***.

Eva001Ikari

iTrader: (7)

.........dizzy right.....

That word, "dizzy" got so god damn annoying while reading these posts, is it so hard to type distributor?

Anyway to answer your question, just go with the single and use the electronic ignition set up from the 82-85. If your worried about being able to adjust the timing from the single unit then i guess you could stay with the dual set up but as far as simplicity goes, its less parts to deal with.

buzz

The twin dizzy 12a was fitted to the pre 1974 rx2's and early rx4's. (At least that was the case in Australia - and in Aussie delivered rx2's they changed late in 1973). Obvious thing... two dizzies. Front cover can be swapped to a single dizzy version, and I've seen a single dizzy fitted to one of the dizzy holes on a twin dizzy front cover.

The rx2 twin dizzy engine used mounts that attached to the sides of the front plate, unlike the single dizzy engines. Some twin dizzy engine and boxes had the stater motor mounted on the top of the engine, coming back over the block - pretty much every single dizzy engine has the starter down under the spark plug side of the engine.

Yes, 6mm seals were usually the standard.

I believe twin dizzy gearboxes were not interchangeable with single dizzy boxes, though the output shaft splines were the same as later ones. Twin dizzy engines had really restrictive exhaust ports, some had 3 holes instead of the large single one - probably to try and solve problems with the apex seal chattering in the surface. I think the inlet manifolds are a different alignment as well.

trochoid

iTrader: (6)

Finally, someone who actually knows the 'facts' and isn't guessing or astounded in wonderment/disbelief, lol. Great job on covering most of the differences. Couple of points, (pun intended) to point out. Electronic dizzys were introduced in 81, the top mounted starter engines would not take the later bottom mount trannys, and the 3 hole exhaust ports were a failed attempt to quiet the exhaust. They were very restrictive.

Back in the same era, an upgrade for V8s was a dual point dizzy. Not quite the same purpose or principle, but as much or bigger of a pita to tune.

jgrewe

iTrader: (1)

Since I've totally hijacked this thread maybe we can keep it going as a good resource. In the vintage racing that I'm restoring my car for we are allowed to replace the points with electronic ignition and MSD's. I have a twin front cover but no distributors, I'd like to make the car as period correct as I can but not if I'm going to kill performance. With electronic ignition would the twins be OK for a bridgeport running around 10,000rpm?

I've got 5 or 6 single distributors laying around and plenty of those front covers. I just want the car to look more like it did when it was first raced.

t_g_farrell

iTrader: (1)

Hmm, 80 was the first year for electonic ignition. 79s still had points. No twin distributors in rx7 for any model year.

jgrewe

iTrader: (1)

I'm doing a 1972 RX2.

BLACKrotor92

iTrader: (3)

im doin a 73 rx2 coupe

Latin270

EDSRX3

Its difficult to find an electronic conversion to fit the twin dizzy(and they have been called that for a loooooong time). There was a system available last century. Best bet may be to have something fabricated using some kind of optical sensor set up!

If you figure something out let me know! I'd love to put a twin dizzy back in the RX3!

I have a box of old twin dizzies hanging around if you want to persue the project and need parts!

buzz

No worries. I qualified most of the things I said because different markets got different sets of options and changes were implemented over differing time frames. Down under, they were not badged or in any way called an RX2 - but rather the rear quarter had the 'capella' badge and the owner manuals called it a Capella RE. I have a November 73 rx2 and it is a twin dizzy chassis, whereas a friend has a December 73 version that were are pretty sure is originally a single dizzy version, complete with the 'dog bone' tail lights.

When did the US market go from what we called the series two to the series 3 rx2? (twin round tail lights, twin dizzy, side mount engine to dog bone tail lights, single dizzy front mount engine)?

While extremely very rare, we did see a couple of the factory delivered sports versions with the dual throat mikuni(?) carbs and bridgeports. Even then, it is hard to tell if they were in fact off the show room floor or came is as a dealer or evaluation special, or as a current-at-the-time private import or even diplomatic vehicle.

The 3 hole exhausts are a nasty looking bit of work, and even then usually had a thermal reactor further choking the noise and emissions. There was a factory extractor unit that I believe was a casting as opposed to a fabrication.

Oh, and some random rx2 p0rn for the freaks:
http://www.ausrotary.com/viewtopic.php?f=3&t=136189

BLACKrotor92

iTrader: (3)

soo a 79 12a frount cap dosent fit a 73 12a motor??

BASTARD

iTrader: (4)

The twin distributor came in all 12a's up to the 73 model year... The 1974 model year changed to the single distributor... Here in the states, a December manufacture date would be considered a 74' model year