wankel=awesome

Well I have this Nikki Project to start in the near future, and I chose this carb to do it with:



However, I have no idea what year carb it is, or even what it came from.

Its missing its main jets, and floats. I have those parts sitting around though.

Some more pics if it helps:

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With top removed

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Shot of the odd FBVS and electronic power valve?

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Another shot of the "power valve"

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Shot of the primary air bleed arrangement for Jeff20b

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Another shot

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Carb with top removed. Has very slightly larger secondary venturi's than my 83 carb.

wankel=awesome

Well i have no idea why all of the pics arent showing unless you click the links, but whatever.

plentymoon

that seriously looks like another style of nikki or well from what I can tell from the few instructions on how to rebuild it.

it looks like an older model of nikki or a rip of version can't really tell since i'm still new to carbs as well but I have gaskets even for that one you have there.

tommyeflight89

iTrader: (4)

I am almost certain this is an earlier Nikki from an RX4 or something like that. My car (82) came with a very similar carb bolted to the original 12A. Also had an intake mani that must have belonged with the carb.

I made a post with pics asking to ID my carb. I'lol find the link.

There is a site that has a large collection of rx7 docs and also stuff for earlier rotaries. The rebuild manual will be there.. just forget the link!

tommyeflight89

iTrader: (4)

http://foxed.ca/index.php?page=rx7manual#rx3

I think it's in the rX2/ service manual. Mine is older because the op oil is dripped into the float bowls instead of the primaries.

plentymoon

Just looked at my rebuild kits instructions that is what you got sir a a nice fancy Nikki carburetor just do what Tommy siad and get the fsm all should be well.

wankel=awesome

its looking like an RX3 carb, for an automatic?

I just figured out what these long rod things where in the top leading down to the mains. Jeff20b commented they were operated by the rats nest and all that, but after playing with the air compressor i learned something else!

Those tubes on top in the secondaries looked like fuel bowl vents, but as it turns out if you blow air past them, it lifts the rods up, exposing these little "40" marked jets at the bottom of the fuel bowl. Its almost like an airspeed operated enrichment system. Very cool.

I have no idea how that would ever work with a turbo though. I'll probably be deleting it

Jeff20B

iTrader: (13)

Ok now that I've seen the top of the carb, and inside, I'm going to narrow it
down and say it is a 1976, possibly J-spec from an automatic.

The thing you're calling FBVS is actually for the vacuum secondary. Check out
where/how it is plumbed.

These older carbs did not have a float bowl vent solenoid because the air cleaner
lids had a charcoal canister built in. Ask divindriver.

The richer solenoid and power valve tell me this carb probably came from an
automatic, but anything is possible. They can probably be removed and the holes
blocked withouit too much trouble, or just leave them in not connected to 12V.
Study whether the little steel pin valve closes or opens when 12V is applied and
use your judgement.

Thanks for the closeup of the primary air bleeds. I see what looks like 190 & 50
slow, and 90 main. Pretty typical. Also pretty typical secondary air bleeds too.

Check your fuel jets. I think you may see 94 primary and 150 or 160 secondary,
as this carb came off of a channeled normal runner manifold from an RX-3, but
could have been an RX-2.

I can tell it's a 76 carb by the fuel banjo inlet/outlet fitting. That is how they did it
back then. Also it has OMP nipples pointing at the boosters, not mounted in the
top like the really early twin dizzy RX-2 carbs had back in 71-73.

Were you wanting to hog this carb out? As you said it always ran great for you.
Better than your '83 carb. Hmm, I say go for it! [img]
https://www.rx7club.com/images/icons/icon14.gif[/img] I don't have anymore old
school carbs. The most oddball carb I have right now is from a 6 port 12A but it
has some strange features so not sure if it should be hogged. Heck I already
upgraded its primary venturis from a puny 18mm to a more usual 20mm. But this
thread about you, so let us know what your plans are!

Jeff20B

iTrader: (13)

Ah, see? I knew it had those rods and the little 40 jets at
the bottom of the bowls (which were not pictured).

I have an 80 top with those rods and I deleted them by first bending them hard
over, so they don't move around anymore, then cutting them off and smoothing
the rest of the nub down where necessary. The result was good enough to use
some RX-3 floats! You know, the realy fat kind. So it's my guess your carb has
the more modern floats with the circular section missing in order to clear the
rods. Not ther classis "RX-3" floats we've all come to lust after.

Just a note, all of my boost prepped carbs have modern floats in them and they
do just fine. Actually, they are a safer option when running boost because these
smaller floats displace less fuel, thus you have MORE fuel available in the bowls
in case the pump sucks an air bubble.

And yes I used my air compressor to blow the water and degreaser out of the
little holes the rods use. It didn't strike me that they were operated by incoming
air pressure. All I knew is if I push on them, milky water would squirt out. Yum!

wankel=awesome

Well I have had a lot of good times with this carb, and it has a ton of sentimental value to me. I've honestly had this carb sitting on one shelf or another since I was 16. It was my dad's first, and he had a 76 rx3 wagon in high school.

I have used it so many times to run many different 12A's and never had to do anything except adjust its idle mixture and it always ran great.

So im going to use it! And maybe if I can learn how to use this enrichment system ill retain it until I go boost. I dont know, but it seems to me like its a cool feature. It might actually be beneficial to forced air, but I wont know until I get it together and start tuning.

I cleaned the jets up and they are marked 100 pri, and 160 secondary. I do believe it was ME who put the 100's in it years ago though. If memory serves me right it had 92 main jets stock.

Jeff20B

iTrader: (13)

Ah, my 76 Cosmo carb had 100 primary jets.

Yeah, prep this carb for boost. Sounds like a cool idea.

wankel=awesome

Dug around for this old intake mani


Shot at the runners. It's stock, but from what ive gathered this is near ideal for the hogged nikki


Minty spacer to match the intake

Jeff20B

iTrader: (13)

What you've got there is what looks like a 79 intake manifold. And yes they work
very well with a hogged Nikki. The result is very crisp throttle response that
makes you question why you ever bothered with a Holley in the first place. Not
to mention the obvious power from idle to redline.

The other nice thing about these manifolds is there is no cover area for the ACV
port in the engine. This means you can take a saws-all and start cutting all of the
ACV casting off that would normally interfere with a turbo. Then use an angle
grinder to trim the aluminum down but not too much as there is a coolant jacket
in there! This is a good excuse to fill the intermediate ACV port with quicksteel
and the coolant ports in the rotor housings with freeze plugs. I'm sure you can
guess by now that that's what I do.

By the way, your manifold is not from an RX-3. Ask glazedham42.

Jeff20B

iTrader: (13)

One more thing. That brass fitting you've got which blocks off the original so-
called altitude compensator hole, is the perfect place to plumb your BOV and
boost gauge.

Get this fitting from RB Heater Water Outlet Plug for 81-earlier rotary engines - Racing Beat

Also get an aluminum crush washer which I don't know if RB sells. They're easy
enough to find.

Get a small NPT barbed fitting with a 3/16" nipple and a 1/8" NPT thread.

Drill and tap the steel mini block off bolt from RB with the correct drill bit and NPT
tap.

I've done this on all my installs. Use stock vacuum hose and a Tee fitting to hook
up the BOV and boost gauge. Couldn't be simpler.

I've got a closeup pic of one installed in an NO manifold which is a similar casting
to your 79. It's not a great picture, but good enough to see what I'm talking
about.

Jeff20B

iTrader: (13)

Since we can't edit anymore for some reason, I gotta make another post. It's to say you may
need to break off the surrounding phenolic material from your spacer in order to have enough
room for a turbo. It'll suck seeing how pristine yours is, but sometimes that's what you gotta
do. You won't know until the turbo is getting installed, obviously.

I had no choice but to remove the surround in my setups as I used an S5 turbo with only a
7/16" spacer and the stock exhaust manifold. It needed to clear the idler arm, so I got a MOOG,
and it still needed to let me install and remove it, so I tested everything with a carb spacer that
already had its surround broken off by a PO. It fit so well with no clearance issues I went with it
on the other installs.

Remember I've got a Hitachi manifold with a Nikki stud pattern drilled and tapped, so its upper
flange area is wider. Some older manifolds also needed channels cut to connect primary runners
to secondaries. I copied the size and shape of channels in the NO manifolds. I know this
doesn't help you specifically, but it shows you're on the right track.

Oh you might want to open up the secondary that's got some casting bumps for the emissions
holes that lead down to the ACV section. Just make the runner round and it won't cut into the
holes at all. Mazda did this for mass production. You can take your time to finesse everything.

wankel=awesome

this will be NA for at least a few months running before I get the parts together for a turbo.

I want an OEM s4 turbo, but I dont have any way to mount one to my 12A.

I have a cartech GSLSE turbo mani in the wings though....

I want to keep this car 12A. I know. Its stupid. But its kindof the soul of the FB.

SO to get this running for NA im going to tune it that way to start, then start the work to go turbo. Right now I have enough work ahead of me just getting the carb together and working.

Any tricks to using the quicksteel to shut the blocks ACV port? I have never used the stuff before, so im paranoid about putting it in there without some research.

wankel=awesome

Also, I know this manifold wasnt from an Rx3, I bought this here on the forums as an SA intake mani a year or two ago.

Jeff20B

iTrader: (13)

I think an S4 turbo and a 12A are a match made in heaven! So don't feel
ashamed about it. The FC turbo is the perfect size for a 12A and kinda small on a
13B. The good thing about an S4 turbo is you can easily hog out the wastegate
hole, which is far more work on an S5. You should hog out the wastegate hole if
you plan tp use any exhaust bigger than 2.5" I'd recommend a 3" DP and then
contract down to 2.5" under the car. Or go full 3" if you like more drone.

Staying NA for a while is a very good idea. I did after the hogging out of the
venturis, to get an idea of basic tuning. It was part of the learning process to
start NA first, then carefully move into boost.

Set about six weeks of time aside for the initial carb work. You don't want to rush
it. Of course you can work at your own speed, but it took me 6 weeks to hog out
and boost prep all four of my carbs. Then I added the '80 carb (with spring
loaded rods and the little 40 jets in the bowls which were all corroded so I didn't
use the 80 main body) with '79 parts onto the end of the production run while I
still had all the tools out and could hog out one more set of venturis. I was pretty
tired of all the work though, but I got it all done. Then I moved on to boost!

Hmm, you should put the quicksteel in the carb first. I say this because the metal
will be clean after you use a degreaser on it, and it's right there in front of you.
This will give you some practice.

As for getting it into the engine, that will be tough because the hole will be caked
with carbon that may have some oil mixed in. I'd get a shop vac out there and a
dremel with a stone you don't care about, and have a buddy hold the nozzle
next to where you're grinding the carbon until you hit fresh iron. This is the only
way I can think of that will give a clean enough surface for the quicksteel to stick.
Then hit is with a little brake cleaner if necessary, but be aware the oil in the
carbon will move once mobilized by the brake cleaner, so a second dremeling will
be needed. As long as you have a rim of fresh clean iron, you can take 1/3 or 1/2
stick of quicksteel, mash it up in your fingers until it's a consistant grey and starts
to warm up, then push it into the hole until it's all in there. Then smooth the
edges over until there are no gaps visible. You're just trying to fill the void with a
big mass of quicksteel to act like a physical barrier to the strong exhaust pulses
that pulse up through there, and to the heat they carry with them. The last part
about spreading the quicksteel against the edges of the ACV port is to try to
make it air tight as much as possible. It should look like this.

wankel=awesome

How do I install an S4 turbo to the 12a?

Jeff20B

iTrader: (13)

That's a really good question.