Rusty Shackleford

im looking at carb kits at racing beat and rotary shack....would a holly or a weber side draft be better??? and if im looking to street port later down the road in a year or two should i go now and get the holly street port system and the 48 or 45 carb??????

FB II

what exactly are the plans for the motor? just a streeport? you gonna be track racing? just a street car?

rxseven07

i have a weber, and i honestly dont like the low end power... plus i dont auto x, and thats what my weber is for, so in the spring im going to sell mine and get a holley... im more of a straight line racer. there was this article in the turbo mag, where it said a n/a 13b 6port with a holley carb and full racing beat header will produce 180hp, dont know if thats flywheel or wheels...

mortenf

Ok, there are several ways to go when choosing a carb.
First, the Holley is a good carb, but it lacks the tuneability of the Webers and the Dellortos.

For original applications, meaning unported, and not a lot of mods, the Nikki modded by sterling is a very good choise. This carb is also good if you want to build the car over time, and throw more money on exhaust, fuel and whatever.
Plus, you can run the original intake.

Sidedraught is the way to go, if you want high end power, but it has to be tuned properly to work the way it was supposed to do. In this case, a 45 is enough for original ports, and even small streetports. Bigger than this, and i would go 48.
Remember, going sidedraught, means you are going to need a bigger fuel pump, fuel pressure regulator, different intake, air filter..+++ The Mikuni 44 is also considered as a good carb, but i have never seen it in person.

If the car isnt ment for street use at all, and you want to do a BIG port job, like bridge or even PP, i would recomend a IDA 48 or even a 51! You will loose out on some driveability, and it guzzles down fuel like a Freightliner, but it will also blow the doors of a 3.rd gen!

I myself have a 4 port 13B, and run it with a Dellorto 45. Its basically the same as the weber, but a little bit more tuneable. Its also a bitch to get parts for...

RX7Elmo

Mortenf has it right on on this one. The sidedraft stuff is known to be better on auto-x track cars, or just cars that will take higher gloads. Apparently for big power, the downdraft carbs are the better choice for the rotaries.

if you are going to streetport your 12a, you'd want the 600cfm holley as well. I believe a 45dcoe flows about 533cfm (not certain) and the 48dcoe flows about 600cfm if not more.\
Weber dcoe carbs have the advantage that they are used in many cirlces and therefore there's lots of spare parts and help out there.

Random question to add...where can you purchase JUST a weber dcoe carb for a good price online?

Rotor13B

That's more than likely at the flywheel. I would get rid of the 45 and go with a 48 dcoe instead.

Blake

A 48mm carb is about the *minimum* you want on a 13B, even with bone stock ports. 44/45s are restrictive. 51 IDA is a great setup on a PP or bridgeport. I disagree entirely with the comments about driveability and fuel economy. My Peripheral Port 13B with Weber 51 IDA got 19.5 mpg on the freeway (~15mpg when pulling a big tire/tool trailer) and had totally linear torque from 4K to 9K, which made it incredibly responsive and well-mannered on the street.

Weber IDA (downdraft) carbs are superior for cornering over their DCO (side draft) cousins due to float bowl issues. The DCOs are more common in street applications only because they have chokes available; the IDA is a pure race carb, in the sense that there is no provision for a choke. I never minded not having a choke because it was easy to start once you had a system (x number of pumps of the throttle and y amount of feathering when cranking).

I don't much care for the Holleys, even though I own two (one's on my F250 ). Even with the Racing Beat modifications, Jim Mederer's own tests showed that it had less HP under the curve than a 48mm sidedraft Weber (it may have been a Mikuni, I forget, but the basic Weber design that they all "borrow"). The Weber made something like 8 fewer peak HP, but it was obvious from the dyno graphs that he had too small of a venturi in it. Even so, the power curve of the Weber was much bolder and the *average power under the curve between shift points* was higher. Further, he had to spend countless hours on the dyno troubleshooting his already modified Holley to get it to perform up to expectations (work that apparently did not get applied to the Weber), which ultimately involved him rotating it 180 degrees from normal. This is all in Drag Sport magazine from a year or two ago, BTW. Also, any Holley used on a rotary is necessarily rotated 90 degrees from it's intended orientation. This can do weird things to float bowls and such, though I don't have any specific examples to site. Let's just say you're asking a straight-line carb to think it's cornering in one direction for an extended period of time...when you are really just trying to drive straight. Maybe it works okay, but that's not how it was designed to operate.

Blake

This statement is wrong. The IDA is an all-around better carb, including in high-G cornering. Autocrossers and road racers have known this for 30 years! The only shortcomings of the IDA are that it (1) does not have provisions for a choke of any kind and (2) can be a problem for hood clearance. This is not to say the DCO carbs are bad, per se, but they certainly do not measure up to the venerable IDA.

mortenf

I disagree that you must have at least a 48! My 45 fitted with 230 jets has no problem overflowing the engine at all! That said, i have a 76-78 4 port, but when we used a wideband 02 on the car, it had no problem fuelwise at all. And i have a mild street port. We have also tried it on a 86 NA, and it had no porblem there either!

But that said, my carb is a DHLA.

If you can get a PP that does 20 mpg, then you are a god, so im not trying to diss you or anything. I werent trying to diss the IDA, i dream about that setup, but they are extremly hard to come by here in Norway..

I still think the basic guide to carbing goes a little something like this:

Original port: Sterling, Nikki, and Holley

Mild Port job, street port: Sterling, Dellorto, Weber, Mikuni

Big street port, Bridge and PP: IDA.

Im not saying that there are "borders" between the applications, of course you can make a holley work on a street port, but i still believe that a Dellorto DHLA would be better and so on!

Now lets get Sterling and 680RWHP in here and let the discussion begin!

Siraniko

iTrader: (13)

That carb is too small. And of course, If you dont have the experience with other carbs, you wont know the difference.

Siraniko

iTrader: (13)

Get a 48 IDA and you wont have to buy a new carb. As I mentioned before, one size fits all.

mortenf

So you are basically saying that the carb on my car is too small, yet it still manages to overflow the engine without any problems, and that the readings we got from the wideband are wrong, because they clearly stated that everything was great?

Well, maybe you are right..

I do want that IDA tough, but i need to get the car out of storage first.. Snow is a bitch..

Siraniko

iTrader: (13)

The only problem with any used carb is the idle mixture screw. Ppl tend to turn the screw too tight which somewhat **** up the hole in the circuit --- with that said, it will make the car run rich due to excess gas.

RX7Elmo

I stand corrected :teeth

Also answer to my other question? where to purchase DCOE carbs online for a decent price...besides ebay?

mortenf

That could be true in some cases, but i got help tuning my rebuilt carb from a specialist, who knows his way around rotarys. (He currently has a 550 BHP dyno proven 12A turbo)

He used the same carb for a 250 BHP turbo application, and the carb had no problem.

Of course, every carb works best when its freshly rebuilt and tuned properly..

rxtasy3

iTrader: (2)

i run the rb 600 holley on my '74 sp 13b and yes the carb sits 90 deg from its normal position as it would on a v8. true it's not a good carb for autox, due to stumble in the corners. otherwise, the carb works great. i can take it thru all gears at wot from a standing start and run that speedo to 130 with no hessitations from fuel starvation. i also run no choke, it fires right up with just one short squirt of the ap. so far it covers the 1/8 mile in 9.38 sec.

diabolical1

iTrader: (3)

i thought the stumble problem was pretty much corrected when using the individual bowl feeds.

FB II

i remember when i tried getting my holley to work on my car a long while back. quite a tuning hassle. it did fire right up and idle'd right off the bat, no choke. soooo much stumbling, but that was all in the jetting and cam adjustment. if i worked with it a bit more it would have been nice. i got rid of it tho, see sig for current setup.

FD Racer

I had bad luck with holleys as well. Straight line was cool, but turns at the track were horrible...even with center pivot float bowls. Having a choke was cool for the street and the secondaries made it easy to tune for WOT. But otherwise, I really did'nt like anything about the holley. Lots of stumbles while cruising/partial throttle, and low end response kinda sucked.
If you have the cash (ie Save your money), go with throttle body injection....best thing I ever did to my setup.

rxseven07

u can buy a lone weber at peircemanifolds.com

680RWHP12A

any aftermarket carb will net better than stock carb performance..the question is , wich carb would be best for your specific application.
i like weber carbs, just because of thier tuneability and adjustability... you can change every circut of a weber to best suite your needs! you cant beat that!!
need more low end, put smaller venturies, need more top end put larger ones, its that easy...want to change your mixture in different rpms? well just swap out the emulsion tubes! and so on and so on......

weber gets my vote!


but if you know what your doing with a holley, they can work pretty good too, look at directfreaks car!!

Rotor13B

Who did you go through for that TB setup?

FD Racer

Xtreme rotaries in Australia. They have me a great deal. There website isn't the best, but here it is...

http://www.xtremerotaries.com/

rxtasy3

iTrader: (2)

oh i do plan on going efi when i get some extra money. the cheapest way for me would be to go with a fuel only ecu, mt-4.

TurboIIGuy

over here in L.A. we have a 12a powered RX2 with a big streetport getting pumped around courtesy of a 51 weber IDA. It runs great. Ever so slightly rich but nothing to toxic. It has racing beat road race headers feeding into dual side by side mounted Magnaflow mufflers. It sounds aggressive and runs great. Good driveabiltiy and incredible top end. we haven't dyno run it yet but it pulls all the way to 8000 rpm which we set as our safe shift point maximum.
the car is here for any local guys that care to see it. It's a blast to drive.
I have a 48 dellorto DHLA on my 84 RX7 right now. My Rx7 has a very small streetport, it was the first motor we ever did years ago. The motor has always run well but I have to say I'm taking off my Dellorto in favor of the stock nikki. The dellorto isn't what I expected it to be and I have heard from to many people that weber side drafts are better and Mikuni is ultimatley the best in terms of overall performance from low end to top end.
My dellorto is nice with its quick throttle response but the car feels so much torquier with the stock carb.
I have an old RX2 carb on the 84 RX7, I also ported out the secondaries in the carb and replaced the throttle paltes to accomodate that mod. And the stock intake manifold was match ported to the intake holes of the motor. As the 84 RX7 is right now with these mods to the stock carb and intake manifold with the streetport and a full racing beat exhaust it is slightly faster than most of the nissan 350z's in my neighbor hood. I can usually stay about half a car in front of them. They will eat me on the launch but I catch up in about 30 feet and move past.
I guess it all comes down to who you ask about what is best for what isn't it...
I haven't tried a holley yet but I would like to see what they are all about.
If anyone wants to trade trix of the backyard tuner hit me up.
I am always interested in hearing what others have tried and share the stuff I have tried.
Peace