I got this carb today, and I have no idea what it's from. Can anyone here tell me what this is? The secondaries have been converted to mechanical linkage, choke has been eliminated, air horn is very shiny. Has some rust, but maybe I can clean it up and rebuild it if I can identify it and get the correct kit.

 

looks like its from an rx2 or rx3

 

RX-2 carb that's been modified.

Get a 79-80 rebuild kit from rockauto. Do not change the needles and seats. Leave the stock ones alone. Only change the site glass window o-rings and gaskets and swap out the accel pump diaphram.

Use your best judgement if you want to change the base plate gasket or the air horn gasket. If they rip upon disassembly, you have no choice, but if they stay intact, stock is usually better.

 

Have so many questions about this carb... What do I need to do to this to install it on my 83 rx7? Jeff20b you said I should try to use the stock gaskets on the body of the carb, why, if the 79/80 rebuild kit will work? What are the three nipples on the carb? Oil metering lines? And whats with the length of the center stud and brass tubes? What are the brass tubes? Sorry, I've been staring at this thing for an hour trying to figure this stuff out.

 

What's the story on the single fuel inlet and no return line? Can I use the steel fuel lines from my 83 carb? What has been removed from this carb? Anyone have pics of a stock rx2 carb? Can I modify my 83 blue air filter housing to go on this carb, or should I put a post on the classifieds for an original filter housing?

 

That's a lot of questions and I don't have a lot of time to answer them.

There are two small nipples on the carb for oil metering located on the "top" or air horn.

The single fuel inlet is fine. No need for a return.

The long stud is removed by a 14mm wrench. Then the stock stud from your 83 carb can swap in so your stock blue air cleaner will fit.

The brass tubes are a racing mod to allow float bowl venting under high "G"s without sloshing down into the 4 barrels.

The small nipple down on the cast iron baseplate is probably not needed (emissions) and can be capped.

 

Wow... Thank you jeff20b!!! Sorry so many questions... I got this carb from a guy who recycles metal, he was going to scrap this carb if nobody was interested! I will try to cut holes in my air cleaner lid to accommodate the brass tubes, sounds like its a mod worth keeping. Will the carb base and air horn gaskets from the 79/80 kit match the original gaskets? I predict the old gaskets will not be usable.

 

i guess question would be is a rx2 carb any better then a rx7 carb?

 

Yes blwfly thank you! In a nutshell, is the rx2 carb an advantage? No emissions required in southern Oregon

 

Trim the lid? What? Just trim the tubes slightly if you have to. Notice their length isn't even identical. So cut them down a little if necessary.

Is an RX-2 carb an advantage? I'd say no but this one has been modified so I'd say yes. Unless the mods make it a lesser carb than a stock unmodified one.

 

I'm looking at rock auto's pictures of their carb kits, none of them look like the gaskets will match. I will try to make my own gaskets for the body, and I have an unopened hygrade carb kit for my 83, which I will get the rest from. Here we go

 

That sounds like a good plan. Remember leave the needles and seats alone because all aftermarket ones in kits are machined incorrectly and lead to constant flooding. Also don't disturb any aluminum crush washers if you can help it.

Here's a great idea. Post pics of the carb with the top off and the underside of the top so we can see how they installed the long tubes. I also would like to see the air bleeds to see how much they may have been messed with.

 

I will take better pictures soon.

 

I'd say whomever modded that carb's top knew what they were doing. It has Grose jets and RX-2 floats which most people like. They don't like boost though, just letting you know.

The rest of the carb looks stock for that era so the only power gains they got were from the air horn work.

 

What kind of needle valve is in the float area? The clear ball is new to me.

 

Grose jets are what the glass ball valve things are called.

 

Got the thing cleaned up and reassembled. Odd thing was, different size secondary main jets and non matching jets and air bleeds, meaning, different but close sizes on front and rear bowls, but the jets appear to be drilled to match. Can anyone tell me what jets and air bleeds are stock on an rx2, and what sizes belong where in the carb body? I made a diagram when I took apart the carb, but it appears the jets were mixed up.

 

I was able to reuse all gaskets without leaks, used a 83 Nikki for reference to bleeder and jet locations, and had to turn my stock air cleaner 45 degrees to get a good seal. I let the fuel pump run for five minutes to let a sticky grose valve free up, and a couple pumps of the gas pedal and it fired right up. Sputtered a couple times on its way to warming up, but now I've got a beautiful exhaust note, smoother revving than any other set up I've used, and I have yet to take it above 5k. Interesting... I notice that I can use the rx2 floats and grose valves on my 83. What can I do to make this carb flow even better now? Trim and polish venturies?
Edit: turning the air cleaner 45 degrees was necessary to accommodate the brass tubes, but now the air cleaners center part that holds the carb center stud is now partly blocking flow into the carb. I need to find a way to chop up the air cleaner and regain a free path for air.

 

Aaaand.. I'm going nuts. It ran beautifully until I got a couple blocks from home. Same issue as with last carb, bowls ran too low and car stalled. Let it sit with key on for a few minutes and it fires up again for a few seconds. When I put the carb back together I used the old accelerator pump gasket. What symptoms occur when that gasket goes bad? Would it stall when I hit the gas pedal?

 

Sounds like your fuel pump to me

 

Took apart the carb top and found the grose jets had become partially plugged. Is there an easier way to clean out grose jets besides letting them sit in carb cleaner? Can they be taken apart and put back together?
I do have an aftermarket fuel pump with a Holley pressure regulator set to 2.5 psi. I will increase its pressure and see if that helps.

 

Sticking grose jets seem to be the issue. I removed the jets, cleaned them, and tried blowing through them. One flows freely, the other opens with a sudden popping sound when enough pressure is applied. Grose jets seems hard to find, so I'll try switching to newer floats and needles. At least I can adjust that kind of needle and seat.

 

That's weird. I thought the point of Grose jets was so they would never get stuck and flood your carb. Oh well. I guess you learn something new every day.

Look for a set of OEM needles and seats. Don't bother with aftermarket because they don't work right. I've already explained this above but it bears repeating.

Hmm, before you give up on the Grose jets, see if you can soak them in brake cleaner. Or maybe that nasty carb dip stuff that eats gum and varnish for breakfast. It won't hurt brass and glass.

 

I will try soaking the grose jets while I try the stock 83 Nikki floats and needles. I found that much of my frustration with floats came from adjusting the tabs, but then I found that the whole issue with those was the floats were bent where the metal meets the plastic of the float, so even when the tabs looked correct, the float height was incorrect.

 

Needles and seats didn't work. And I soaked the grose jets for nine hours in carb cleaner and now the damn things won't shut off, and I'm flooding. I'm about to throw beer bottles. Just need to find beer first... Tomorrow I'll try adjusting the floats one more time in this little freak.