Inliners International Forums General Discussion Hi Performance WHICH CARB?

HI DUDES, WICH CARB DO U RECOMMEND?

1. EDELBROCK 500 4BBL.
2. HOLLEY 390 4BBL.
3. HOLLEY 390 2BBL.
4. HOLLEY 570 AVENGER 4BBL..

WITH THIS SETUP:
1. LONG TUBE HEADERS.
2. CRANE CAMS POWERMAX CAMSHAFT .467-.498
3. Offenhauser intake. single 4bbl.
4. HEI ignition.

THe idea is for street pourposes...

Thanks a lot for your valious info, time and generosity.

All are a good carb. I happen tolike my holleys. and their are others who like the edelbrook and feel it is more street tuneable. all the carb are with in a good cfm range and will work very well on the offey. Hope this helps }[oooooo]

IVAN,

I have literally the setup that you have. I went with the Edelbrock 500 cfm 4 barrel and it works well with the other components. I have the stock deep dish pistons, which don't give quite the compression I need to make the most of the 4 barrel but it doesn't have "bogging" problems either.

I think the 390 cfm Holley 4 barrel would be a better match for a mild 292 than the Edelbrock but it seems to be more expensive and (from what I've read of others) more difficult to tune. I know the Edelbrock I have is a gas hog - even with overdrive and 3.73 gears (turning about 2050 rpms at 65) I can still only manage about 15 mpg in a not-so-heavy 1966 shortbed stepside truck! So if you get the Edelbrock tune, re-tune and tune some more (probably want to go at least "Stage 1" lean) until you get the MPGs down to an acceptable level.

-magic mike-

I too like the Edelbrock 500 for a lot of reasons but the 390 Holley 4 bbl is popular as well on our inlines. The carb I would not use is the 390 Holley 2 bbl because the number is the same as their 4 bbl but it is all flowing through only 2 venturies where the 4 bbl runs about 1/2 that throught the primaries and won't allow all 390 cfm until the secondaries are also opened. To compensate for the large "holes" you will have to jet the 2 bbl richer and give it a larger accelerator pump shot than the same sized 4 bbl to keep the air fuel ratio near what makes the engine run correctly. This will end up having poorer gas mileage than if you ran the 4 bbl.
Flow rates for 2 bbl and 4 bbl carbs are not figured at the same vacuum readings so it gets more technical than what I just mentioned but the end result is still the same. The 4 bbl will end up being an all around better choice for a street driver.

Mike

CARB PRICES AT SUMMIT:

1. HOLLEY 390 CFM 4BBL - $ 296
2. EDELBROCK 500 CFM 4BBL - $ 276
3. HOLLEY 570 CFM STREET AVENGER - $360

In terms of Price, Tuneability, Gas Mileage, Which do u Consider is the best option guys?...
DO Exists a big difference between manual or electric choke?

Thanks a lot for you replies.....

I say when in doubt, go smaller on the carb. Especially when all you're running is a mild cam, stock rotating assembly and pretty much stock head. There's simply no more need for a larger carb on a six cylinder engine.

I opted for the 500 cfm Edelbrock only after hearing that it was easier to tune than the Holley and finding out that you can generally get them cheaper. Once I talked with Tom Langdon and got his "blessing" of approval with my setup them I went with it - Tom doesn't care for the 390 Holley anyway, for some reason. Still the Holley 390 would be a better fit "on paper."

-magic mike-

P.S. Check Ebay before you buy from Summit. I paid $250, shipping and all, about 3 years ago for my Edelbrock 1403 (which has the electric choke).

Something I don't hear enough about on most threads or conversations about carbs is this: A bigger carb will produce more horsepower, but it always does it at higher rpm's. In other words, the bigger the carb, the faster you have to spin the motor to access the added horsepower. With a relatively stock motor a 500 cfm carb is probably not the best bet. Here's an example. A stock 250 with no changes except a glasspack and a Holley/Weber 5200 will float the valves in first and second with both a saginaw or a muncie 3 speed. So with a carb that's only 270 cfm when measured by 2 barrel standards will turn the engine high enough to run out of camshaft before you run out of carburetion ability. On a set up like we're talking about here I would go with the 390 Holley or else a pair of carter YF or weber carbs. The 500 cfm edlebrock may be okay, but CERTAINLY nothing any bigger. That's just my opinion anyway.

Boo

Magic,

Are the Edelbrock secondaries vacuum or mechanical? Summit says they are 'air valve' secondaries, which I assume means they are vacuum...but you know what they say about assuming.

the throttle blades are mechanical. but the air valve is vacum operated. i have a 390 to sell if needed, it just needs a kit thrown at it. if interested email me telowe2000@yahoo.com. tom

Ok so with the replies I see, the best option could be the 4bbl 390 cfm holley, is it to hard to tune it?, I'm amateur guys...

try this. Get a Holley book. Be methodical. You can do it....mutt
http://www.bob2000.com/carb.htm

Wide,
The throttle blades are mechanical, but the air valves are operated by the amount of air passing through the carb. and over the air valves. Holley uses vacuum to activate a diaphram that pulls the secondaries open. The Edlebrock, or any carb, with metering rods will meter fuel better at part throttle operation.
Jim

Ahhh - OK. Thanks a ton, Jim. That sheds a little light on why some folks have had problems with the 390 and maybe why Tom Langdon feels it's too hard to tune for street use. (Although like Magic Mike, 500 cfm just seems to me like overkill on a little inline. In my case, a 230.)

Well this is so problematic, some of you say that holley 390 cfm its too hard too tune for street use and tom Langdons feels that too, other says Edelbrock 500 4bbl is best for tuning, and what about gas mileage?, I'm so sorry with this dumb questions but I need your vast knowledge to make this work very good, I want gas mileage, good carb tuning and increase of my 292 performance...
Thanks guys a lot.

It's not just a matter of matching up numbers to numbers when selecting a carb and then deciding one is too big or too small. On a stock 250 a 390 Holley might be too much and yet on a well built up 230 a 500 Edelbrock might not be enough.
Things like compression ratio and volumetric efficiency compound the situation along with everything else that has been done to that engine.
Another thing you have to consider is just how often and for how long will the engine be running wide open at xxxx rpm and actually trying to gulp down 390, 500, or 600 cfm? Reality is that most of the time the street engine is being operated on its primary throttle plates and the total cfm of the carb is not a factor. Only at wide open throttle will the carbs max CFM become a factor as to the engine getting too much or not enough air and fuel.

I believe most people are giving you their real world experiences as to which carb works best on their engine. Don't let only numbers be the final decision when selecting a carb.

Mike

Ivan: I have a mildly built 292 --(.030 overbore, bigger intake valves, Crane cam, Rhoads lifters, Offy 4-Bbl intake, Clifford headers.) I have the Holley 4160/8007 @ 390 CFM. I've had this same carb for 28 years (incl. 2nd engine). I have a friend who's an old school Holley fan, so he tunes it for me -- I don't dare touch it myself. Right now, I've gone to a later opening power valve [6.5"Hg from 8.5"Hg] and the 50CC accelerator pump. We're still not sure if the baseplate is warped after all this time. A new one is about $130.
I have Carter AFBs on 2 other trucks with V8s, 600 CFM on a 350, and 750 on a 454. Since Edelbrock has taken over marketing of these carbs the price has gone up and the outside finish shinier. Carter used to make a 400 CFM AFB carb, but Edelbrock doesen't sell these, so they must be obsolete. I like the AFB-type because it has no fragile power valve, is less like a swiss watch, and I can rebuild it myself.
If you want the 500 CFM Edelbrock AFB, Jegs,
www.jegs.com
has them for less than Summit. $225 for the Edl 1404 500 CFM AFB w/manual choke. $289 for the 8007 Holley 390 4160; other carbs from Jegs' I might consider for my application [which is close to yours] are a Holley 450 CFM chokeless 4Bbl [510-O-9776] for $189, and a Road Demon Jr 4Bbl 525 CFM vac secondary, w/ manual choke for $260.
Running my engine build data on one carburetion website, it came up with 406 CFM as the ideal flow for my set up. But in the old school, they used to beat into our heads, the maxim: "less is more."

HEy Dudes, what about to Put a Rochester QUADRAJET carb?, I read about that a quadrajet of 750 cfm is the best option to put in a inline six cilinder because their primaries, or something like that, what are your opinion?

Hi Ivan,

Well, The q-jet will work good when you are on the small primarys. Unfortunately, the secondarys will never open fully as you just don't have enough air flow on a low revving inline six to open them. That is why some think they are working well on their sixes. Another way of saying this is: a q-jet is just too big. They are either 750 or 850 cfm and that's just to much.
(I can hear the protests now )
Jim

Well I read that theory of the Quadrajet 4bbl in this page, SO Give me your opinion, I was so glad to buy a quadrajet too much cheaper than the edelbrocks or holleys, hahahaha.

Check the site:
http://www.mergetel.com/~fraso/RasoEnterprises/Carb-New4bbl.htm

Ivan,

Did you see this? "I know the sound the carb makes when the secondary air valves open up on the 350 but I didn't hear it anything like it on the short drive I made to test it."

The AFB's I've seen were not square bore, but spread bore carbs just like the Q-jet. If you have room - go for the Q-jet as you seem to want to do that. They are good carbs. A bit tough to find parts for and a PITA to work though.
Good luck,
Jim

Mopar's used a similar carb to the quadrajet,(being a spread bore)They were called thermaquad's & I believe they were 800cfm or maybe a little bigger. AFB carbs had vacuum secondaries,weighted secondaries.or Carter carb called the AVS,the secondaries had an adjustable spring.I tried a Carter AFB 450,it ran OK on my 250 ,but nothing compares to running three sidedraft Webers.
I also ran Holley 350 two barrel,just OK,650 Quadrajet,just ok,625 AVS Carter just Ok. Running Side drafts Webers are awesome,just time consuming with jetting them.It is really a day & night difference!

The Carter AFB is a square-bore, the AVS has a spread bore, but not exactly the same as the Q-Jet. I have seen pix (in Santucci?) of a GM factory 250/292 iron intake for a 4Bbl Q-Jet. Also the old Pontiac Sprint OHC 250 L6 was sometimes set up for a Q-Jet. Maybe in Latin America, where alcohol is the fuel of choice, bigger CFM needs are encountered?

I believe the AVS carbs are square bores. I owned three of them. The Pontiac 6 cylinder Quadrajet I believe was a 650 CFM. I consider spread bore carbs w/small primaries & huge secondaries like the quadrajet & thermaquad. You cannot bolt on a Carter AVS carb onto a spreadbore manifold unless you get an adapter plate.