4 barrel question, is spread bore better ?

[DaveB]

I just got a really nice 401 from a 74 wagoneer and it has a new Carter AFB competition carb on it. When I took off the carb to keep it safe while taking the engine out I noticed that the intake manifold was not a spread bore but had four equal sized holes. The 360s in my CJ7 and wagoneer both have spread bore manifolds. So which is better ?
Also is the carter carb any good off road ? or should I find something else ?
Dave
77 cj7, 88 wagoneer, 86/92 cherokee, and too many spare parts

[Damage, Inc.]

Strictly from a technical point of view, square bore is better for off-road purposes. The spread bore is intended for more 'wide open' use.

Hope this confuses you more...err...helps you... smile.gif

[mechanic58]

Well I suppose it's just a matter of opinion. I know MOST people don't even like to hear the word QUADRAJET, but they're really good carburators so long as you know how to tweak them. I'm an avid dragracer and I've run 12's with a q-jet before. I've also gotten 20 mpg with one on a 350 in a suburban before too....just some food for thought. OH YEAH, almost forgot....there's nothing more fun than scaring the Great Googley MoogleyGreat Googley MoogleyGreat Googley MoogleyGreat Googley MoogleyGreat Googley Moogley out of some poor unsuspecting pedestrians with a little W.O.T. action in low gear with your q-jet.

[porkchop]

Matt, are you going to Ouray? I can sure use some help tweaking my q-jet. :D .

[mechanic58]

Unfortunately I am not...sorry Porkchop. It's good to hear that I'm not the only Q-jet fan though. For a good many years I was thinking I was. LOL. If you have some more specific questions about your q-jet, I'd be glad to help you. I check my email daily, just be sure to make a subject line I'll recognize.

[davez26]

I don't believe that either is inherently better, but for off road use, I'd say the spread-bore has an advantage. Here is why. On the square bore, the holes are of equal size, and on the spread bore they are not, the primaries are much smaller than the secondaries and are even smaller than on the square bore. So the spread-bore would have a slight edge on low-speed throttle manuevers. I'll try to explain, or make a fool of myself. The smaller the throttle valve opening, the more intense the vaccum signal will be at the venturis. This where the fuel flow is affected. A carb on a smaller opening will be more responsive than on a larger opening with the same carburetor. It's like a controlled vacuum leak. A large vaccum leak somewhere you can't feel by hand, but if you put your finger on the end of a vacuum hose, you can feel it! and that is what makes fuel flow. Kinda the same principle behind picking the correct size carburetor. To big carb=poor low speed throttle response, pretty good top end. Small sized carb=good low speed throttle response, poor top end (the engine starves for fuel). It's all about controlling the vacuum. The Quadrajet works around this by having a small primary area, for excellent low speed response, and a large secondary area, for excellent high speed, (power), response. I think that either maifold will be acceptable, as long as it is matched to the carburetor and the carburtor is matched to the intended use. The Carter/Edelbrocks are supposed to be pretty good with the off-road needle and seat.
As for me, count me on the Quadrajet with a spreadbore team, I've had 'em on GM's before, and am in Love with it on the Jeep.

[heydave]

Originally posted by Matt Workman:
there's nothing more fun than scaring the Great Googley MoogleyGreat Googley MoogleyGreat Googley MoogleyGreat Googley MoogleyGreat Googley Moogley out of some poor unsuspecting pedestrians with a little W.O.T. action in low gear with your q-jet.Oh Yea! BAWOOOOP
I miss my Olds 455 powered Chevy pickup.
Maybe I'll put a Q-jet on my 360.

[Damage, Inc.]

Alright dave....you just contradicted yourself in the same paragraph...English 101 is where I'd start!!! smile.gif

[porkchop]

Where was the contradiction?

Can any of you help me tune my Q-jet? If so email me please and I will call you for a step by step over the phone. Thanks.

[davez26]

Where did I go wrong? Am I making any sense? I got my education right here, sorta, I went from K-12 all out in Falcon. Yes, that was after we had the one-room school house!

[heydave]

Originally posted by Damage, Inc.:
Alright dave....you just contradicted yourself in the same paragraph...English 101 is where I'd start!!! smile.gif ???
:confused:

[Damage, Inc.]

Oops...I misread sentence #3...I'll go grab my Eng 101 book!! :(
Feel free to buy me lotsa' beer at Ouray and explain sentence diagraming! smile.gif

[real4wheeler]

To support my drag racing and four wheeling habits, I used to do "super tuning" after hours on mostly GM vehicles.

I can offer about 15 years of advice, but I will tell you that not having the vehicle in front of me may make for more educated guesses than anything.

By the way, I am putting a Q-jet on my Wag this week, and I'm disappointed in how the popular Q-jet adapters seemed to disappear from the auto parts stores. The correct fitting ones, I mean. I realize carbs are old, but I want everything to stay the same as it used to be.....

e-mail me direct: reno1@continet.com

PS Spreadbores have always been known for their better low-end response. But after owning 74 different vehicles, I can say it really doesn't matter much.

[Bob Barry]

Back to the first post, I'd say the squarebore MANIFOLD on your 401 is far superior to the spreadybore, because that Jeep spreadbore manifold is for the oddball Motorcraft 4350 carb.

Even if you wanted to use a Quadrajet (I've got two cars with them myself, so I'm a fan), it would be easier to fit them to the squarebore manifold than to the spreadbore. I put pictures up to illustrate this:

http://home.off-road.com/~wagoneer/tech/carb/4350_compared.html

[DaveB]

Thanks for all of the replies. I have a spread bore manifold on the 360 in my 77 CJ7 and it came with a worthless 4350 carb. I found that all of the adapters that were available didn't fit well so I had a friend at a machine shop make me an adapter for a quadrajet that mathes the patterns up exactly. He entered the gasket patterns for the 4350 and the Qjet into a computer controlled 3D milling machine and blended between the two. It has worked great.
Dave

[ironroad29]

pork chop me and workman grew up togeather and really worship q jets ..as a matter of fact my e mail i q_jetfantasy@hotmail.com .lol i love em wouldn't take anything else people hate em cause thay don't know how to tune em i'll start another post and try and help you with yours

[nightflyers]

I have been running a Q-Jet a Edelbrock Performer manifold since I rebuilt the engine in my first Jeep. I love it. Some people say they are easy to adjust but I found it to be a PITA. I'm not an expert though when it comes to carb adjustment. Took awhile but when I got it, it was worth the hassle

[ironroad29]

yup plus 4 wheel and offroad did a heads up real world comparo on the holly edelbrock and q jet and the q came out on top !! RODCHESTER RULES BABY !!!

[FrankenJeep]

Originally posted by DLyons:
</font><blockquote>quote:</font><hr />Originally posted by Matt Workman:
there's nothing more fun than scaring the Great Googley MoogleyGreat Googley MoogleyGreat Googley MoogleyGreat Googley MoogleyGreat Googley Moogley out of some poor unsuspecting pedestrians with a little W.O.T. action in low gear with your q-jet.Oh Yea! BAWOOOOP
I miss my Olds 455 powered Chevy pickup.
Maybe I'll put a Q-jet on my 360.</font>[/QUOTE]My 455 Buick was more like DuhWHOOOOMMMM. Matbe I needed to tune it better ;) . You forgot to mention that it really impresses the ladies on cruize night in High School.

72 Buick Skylark Sun Coupe, 10 bolt limited slip, 455cid built to Stage I specs ... the ultimate sleeper. I embarassed many a Camaro/Mustang/Chevelle with that one.

Frank

p.s. I've run both Q-jets and Holleys for performance. Personally I like the Q-Jet ... but then again, I prefer Del'Orto's on motorcycles too ... tongue.gif

[ironroad29]

sounds like the secondary air door spring needs tightened woop woop WOOOOOOOOOOOO

[mechanic58]

There ain't nothin that'll make a q-jet sing like a nice crisp Cadilac 500 cubic inch v-8.....those things actually had mufflers on the breather snorkle to cut down on the noise inside the car. Take the breather off and romp on one of them things and you'd swear it was about to suck the hood down on top of it. LOL.