4 barrel carb size

92XJT · 11-25-2009, 02:03 PM

Slowly building up my 360 for my CJ. The motor is, for the most part stock from what I can tell - rebuilt years back and has approx 25k miles on it since rebuild. I just got an offy 4bl intake, and now shopping for a carb. What is an ideal CFM size for this motor? For the most part it will be a trail rig, maybe some highway usage as well. Only other planned mods besides carb and intake will be headers.

my-jeep-earl · 11-25-2009, 02:41 PM

Go to Jegs.com or Summit.com, they have a "calculator" type set up to determine what carburetor to use, good luck.

zaxrubiunl · 11-25-2009, 02:47 PM

are you more of a carter/edlebrock fan, or holley? i'm sure the 1406 edlebrock is gd all around,ive always liked holley 650 mech. choke & secondaries

texasimport · 11-25-2009, 03:10 PM

If you get the Holley TA be sure it is a 90670-2 not a -1 or earlier with out any dash number. Rumored to have issues.

deadeye · 11-25-2009, 03:23 PM

I would stay in the 470-500 cfm range at the most, anything bigger is going to be to big.

92XJT · 11-25-2009, 03:46 PM

thanks - I found an edelbrok 1406 for a very good price, but was thinking 600cfm may be too big for an almost stock motor. Though I did run the same carb on an old 78 gmc with a 350 with no problems. As for brand specific - I have no particular.

Big_Pete1999 · 11-25-2009, 04:23 PM

I'd say 500cfm get an edelbrock

**OlivergreenCJ7** · 11-25-2009, 04:41 PM

For offroad use you'll be unhappy with a eldebrock even with spring loaded needles and seat. The carb doesn't have high vent lines so it easilly floods out in off camber situations in the rocks. I have a 600CFM on a 304 with eldebrock intake and full length headers. It drives extremely well on road, but is way to much for offroad use. I wish I would have went the 470TA route or saved up for a TBI system. I mainly drive my jeep offroad to and from the park and around town. You can get the eldebrock to do better offroad with a fuel pressure regulator running about 3.5 offroad and 5.5 psi for the street.

zaxrubiunl · 11-25-2009, 06:24 PM

ive never had issues w/either being too much ,but theres always variables. i've run 360's & 401's w/ performer intakes, amc heads flow great .

jeepdaddy2000 · 11-25-2009, 10:07 PM

Lower RPM motors respond better to smaller carbs. The size of the carb should get bigger as the size of the motor gets larger or the power band goes up (higher RPM's in smaller engines). A 400 to 600 CFM vaccum secondary carb will work well in your application, with the low side of that spread being a better all around preformer. This will keep the primaries small for low end response while flowing enough higher up. The vaccum secondaries will only open when needed and only enough to cover the engines demands.
The only caveat to this is the Quadrajet. IMHO the best carb out there. Unfortunatly, it only comes in 800CFM or larger. The spreadbore design incorperates the best of both worlds. Small primaries for low end response coupled with a large flow for those high end needs. It also has both the primaries and secondaries running on stepped rods which deliver precisely metered fuel throughout the operating band.

redbird2289 · 11-25-2009, 11:34 PM

Holley makes a "Truck Avenger" carb that i used on my K5 Blazer that worked well. So w/e cfm you chose look and see if they make it.

starfire340 · 11-26-2009, 06:32 AM

Hey jeepdaddy2000....no disrespect, but are you sure about that cfm size for a Qjet? I believe that it came factory on 327's and certainly 350's, but in a stock form of either one of those engines, I can't imagine that they would be able to handle anywhere near what a 800cfm carb would put out for fuel???

**swatson454** · 11-26-2009, 12:28 PM

Quote:

Originally Posted by starfire340

Hey jeepdaddy2000....no disrespect, but are you sure about that cfm size for a Qjet? I believe that it came factory on 327's and certainly 350's, but in a stock form of either one of those engines, I can't imagine that they would be able to handle anywhere near what a 800cfm carb would put out for fuel???

He's right, they're huge

Weber Carburetor

**Mike Romain** · 11-26-2009, 03:06 PM

Quote:

Originally Posted by swatson454

He's right, they're huge

Yup, they are rated 750-800. the nice thing about them is they only use what the engine can suck so one site says anything from a 231 to a 400 ci on the same 750 CFM Q-jet. http://www.carburetor.ca/carbs/tech/Rochester/Quadrajet-index.html

texasimport · 11-26-2009, 06:43 PM

If you want the Holley TA they come 470, 670 or 770 CFM. The 470 is really meant for a 258ci according to Holley tech support and it also states that on the box it comes in. The Holley web sight says otherwise but this is not correct according to them. The 670TA while called a 670 really has effective CFM capability closer to 600 also according to them.

Soooo. . . .if your a Holley guy stick the 670 TA on your 360 and don't look back.