I have a 85 rx7 with a 12a and I'm considering replacing the original carburetor. The question is what is the best replacement carburetor with the least amount of modifications?

 

Why do you want to replace it and what is your goal?

 

You can easily get Holley, Weber, Dellorto, or a Paul Yaw or Sterling modified nikki, all of which will bolt right in without any "modifications" by the end user.

The only thing is that you'll definitely have to do a certain amount of tuning yourself. A good aftermarket fuel pump, fuel pressure guage, and pressure regulator are definitely required for any nikki other than the stock (and are even recommended for the stock one if you've got the time and money).

Whatever your goal with your car is, there's a matching carb out there for you, you just have to be willing to get your hands dirty (so to speak) and learn how to tune it when you get it. If you want a "slap on and go" carb, you're probably not going to find one that will give you what you expect out of a performance carb, but that little effort tuning can make a world of good change

Jon

 

Thanks for the reply, I just priced a Holley with the intake at RacingBeat.com and the cost is approximately
$800.00. I'm just wondering if Holley is the best carburetor for this motor?

 

I continue to have problems with the original carburetor. More power is fine but, dependability is what I'm hoping to accomplish.

 

if you want power then the ultimate carb is the Weber 48 IDA. I think that it is cheaper too!

Dependable too!

 

Thanks, I'll check it out.

 

yeh i heard great things about the 48 IDA weber..

 

Isn't the 48 too big to just slap on a stock port?

I'd say that if you just want a dependable carb, take the one you've got and send it off to Carl and Sterling. Get them to do the rebuild on ya, and when you get it back, do the emissions removal tutorial. That'll get rid of a whole slew of problems, and not knock such a huge hole in your pocket

Jon

 

48 is not to big for stock. 37-39mm chokes are typically used for a 2bbl stock port.

Yes, I changed the fuel filter on my 99 Isuzu Amigo this year. rx7 gets one soon. REPU once I've installed and run my restored fuel tank.

 

...just cause I'm selling carbs does'nt mean I'm gonna stop answering questions like this one...

Here's my opinion-

First thing you should do is purchase and install a fuel pump, fuel regulator and gauge. Replace the fuel filter, too.
The pump should be a 7 pounder, and the regulator should be a 1-4 psi. This regulator will work well with your stock carb, and a Weber, too. De'Lorto and Holleys want to see 6. If your carb choice demands higher flow, a regulator really is'nt that much money.

If you either don't have the money yet, (typical situation for most of us) or you just have'nt made up your mind, you can have fun doing some simple mods to your stock carb. This helps educate people about carbs, too.
If you don't have a free flowing exhaust system, you will not reap the full benefits of any performance carb that you install.

You seem like the type that does not want to dick around too much with the carburetor. (Please take no offence; it's not a judgement.)
If you are'nt into tinkering with tuning and air bleeds and fuel jets and all that stuff that some of us live for doing, then a ready set Holley from RB might be a good choice for you. You cannot simply buy the same carb elsewhere and slap it on, as they reconfigure them specific to the rotarys' demands.
A weber would be another good choice, but more money, I think.
...and not as a business plug, but Carl and I are working on trying to define "levels of modification" for folks so we can appeal to a wider range of needs and budgets.
I don't know about De'Lortos, as they have stopped making them. I don't know about the availability of parts. But basically, your two barrel carbs will yeild the same high end results when tuned properly. They are best if you mostly drive in a higher RPM band than say a Holley 4 barrel. (-they flow as much, but need flow velocity to draw out the proper mixture)

Whatever carb you choose, you WILL have to do some tuning on it. And no matter which one you end up with, you'll have to learn how to finess the throttle and just when to shift in the RPMs to get the best performance.
None of the choices out there are particularly bad.

 

Basically, I think if you are going for bang for buck. I would think the $300 for the modded Nikki would be the cheapest, also considering you wouldnt have to buy a intake! Which will really save some cash.

Hmm, $800 Rb Holley set up, compared to $300 modded Nikki? you be the judge? $500 for other mods, sounds like a bargain to me! Plus if you dont like the Nikki, send it back and get your cash back! I have a feeling you wouldnt be sending it back?

 

As soon as I get the cash I'm sending my Nikki to Carl. I'm looking for bang for the buck and dependability.

I used to run a Mikuni on my SP 13B years ago- it was ok but acted up when the weather/seasons changed..

I have a Weber 45 DCOE now on my stock port 12A and can't seem to tune a stumble out at cruising speeds. From what I can tell/read through these forums, the performance gains from a Weber 45 and a modified Nikki should be very close (but the Nikki is a helluva lot cheaper).

 

Tom:

I would be willing to bet, if you street ported that engine it would get rid of the stumble. I could be wrong, but when I had my Holley set up on my stock port 12a it had a stumble that vanished when I dropped my SP 12a in with everything the same but the ports!

Did the Mikuni scream like hell on you SP 13b? I had a SP 13b with a stock Nikki with bigger jets only and it would run like hell, alot better than my current set up! It was a real screamer ! ! ! I wish I could get my Holley to run the way it did!

I dont know anything about Mikuni's, wassup with them? Are they a big 2 barrel like Weber's and Dollorto's?

 

The Mikuni 44 is a twin barrel progressive sidedraft like dellorto and weber. It was a pretty nice set up. The motor was built by Nick VanNugteren of Rotary Reliability and Racing (I think it's Fast Freddies now).

I'm not sure about the Weber 45. Everyone I've asked has said it is way too small for a SP 13B. I think if I ever do another 13B Sp i'll go with a weber 48IDA (if the Nikki can't be modded, that is).

 

About how much would these three things be, what companies are best, and where can I get them for the cheapest.

 

Fuel pump- Carter 7lb, 92gph. Summit sells them for approx $60? Regulator- Holley 1-4psi, again summit $22. Gauge. Find an industrial supply house and fond a 1-5 psi gauge, forget about anything made for cars. Their range is too high and they are inaccurate for the most part. If you do a search here for carter fuel pump, you should find earlier posts listing the part numbers summit uses.

 

I rebuilt my stock 12a carb and polished the intake manifold. Wow what a difference! It feels like im running a new carb.