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2 BBL v. 4 BBL w/ Quadrajet
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Author:  aspen76 [ Tue Jan 10, 2012 4:44 pm ]
Post subject:  2 BBL v. 4 BBL w/ Quadrajet
Hello (First post!)

I have a 1976 Dodge Aspen with a 225 /6 that I use for a daily driver. The problem is that my daily route involves merging onto the highway. My 1BBL'd Slant just can't get to a good merging speed before the entrance ramp ends. I'm thinking this is due to having a the stock Holley 1 BBL.

I'm looking for more power but without sacrificing a lot of economy. (Currently I get around 19 mpg) I've heard a lot of good things about doing a Super Six conversion. The thing is that I already own a Clifford 4BBL intake.

So I think my options are sell my 4BBL manifold and pick up the essentials for a super six conversion (2BBL manifold, kick down cable, etc), Stick with 4BBL manifold but find an adapter down to a 2 BBL do a super six conversion, Use the 4BBL manifold and pick up a small 4BBL 390 CFM Holley, or Use the 4BBL and pick up a Quadrajet (I mention this option because I've read that it acts like a small 2BBL until enough throttle is applied where the larger secondary open)

So, I'm wondering which option would preserve fuel economy but give me enough power to not get creamed while merging onto the highway? All help is greatly appreciated.
Author:  Rug_Trucker [ Tue Jan 10, 2012 5:16 pm ]
Post subject: 
There is a bunch of small Carter 4bbl's out there. You can pick up a 4131AFB that has Mopar type linkage. 400+cfm. You can buy complete ones for $45 all day long.

Some Qjet's are probably 735cfm. The air door on the big side will regulate air flow. I know the Thermoquad secondary air door will automatically adjust the air flow via engine demand.

The Holley? I have stayed away from the 4bbls. since 1977. Lots of knowledge out there about them.

I wish the AVS was built in a 400cfm size.

If you can find a 273 HP carb it is the same size as a Hyper Pak. I have a 340 Buick AFB I was going to build for my Duster. I sold the Offy intake.
Author:  Jeb [ Tue Jan 10, 2012 5:21 pm ]
Post subject: 
Ever thought about buying a small 4-barrel and unhooking the secondaries?

I've always held the Q-jet in high respect. I suck at tuning them, and parts are a total crapshoot, but when you get one setup right they are pretty much perfect. GM put a lot of $$$ into that carb design, but good Q-jet guys are hard to find nowadays.
Author:  Rug_Trucker [ Tue Jan 10, 2012 5:26 pm ]
Post subject: 
Come to think of it GM used to have Qjets on some truck V-6's! That was just before they went to TBI.
Author:  supton [ Wed Jan 11, 2012 5:41 am ]
Post subject: 
How much tuning is available in the (?) Holley that he has already? I am wondering if exhaust work would be advisable first, get it free flowing; then sort out any timing issues, and then tune the carb he has. None of which would negate doing a 4bbl swap later.

aspen76, it sounds like it is in decent tune (19mpg ain't bad) but can you describe the rest of the setup? Catalyst/no catalyst?
Author:  Rug_Trucker [ Wed Jan 11, 2012 6:16 am ]
Post subject: 
Holley 4bbl jets fit that carb. Probably more is easily available for it than a BBD.

A BBD only adds 15hp. Please correct me if I am wrong.
Author:  Aggressive Ted [ Wed Jan 11, 2012 1:29 pm ]
Post subject: 
Aspen76,

The carb flow may not your problem. I have a single barrel Holley 1920 on my 74 Dart Swinger and can merge (on a short ramp) at any speed the traffic dictates. When no one is around I can merge between 70 to 80 mph with a stock 1979 engine and a 2.76 rear end ratio. It is a very spunky car even though I have a stock 79 engine it at the moment.

A good tune up including setting the valve lash (if yours is still mechanical vavle train), adjust the kick down linkage, a carb rebuild and a distributor recurve will help a lot!

Click on the red link below my name to view photos.
Author:  aspen76 [ Fri Jan 13, 2012 3:11 pm ]
Post subject: 
Hey guys, Thanks for all the posts, I really appreciate all the help.

There is a catalytic converter on the car that I’ve been wanted to cut off since I got the car but have been putting it off because I don’t want to cut it out and re-pipe down there if I end up getting headers or something along that line. (I’ve been told that if I use the Clifford intake that I need to use the Clifford Headers because the headers are made to export exactly what the intake is made to import)

So it’s sounding like I should pursue a small 4BBL since I have the manifold. Thanks for the warnings on the Holley 4 BBLs being bad. There are quite a few Rochester Q-Jets on ebay that are cheap (but need to be rebuilt). Would I preserve more economy with a Q-Jet (even though they’re 750 cfm) or with a small 4BBL?

I rebuilt my 1BBL about 6 months ago (which didn’t work, so I had my mechanic re-do it for me :D). I’m going to do some research to figure out and try to do the things that you suggested Aggressive Ted. (I’m really new to all this so I’ve been doing a lot of research and it looks like I’ve got a lot more to go :D)
Author:  Aggressive Ted [ Fri Jan 13, 2012 5:57 pm ]
Post subject: 
At the age of your car the "cat" could be plugged which at sometime may have overheated your engine and cooked the top end.

A plugged cat can reduce your performance like stuffing a potato up the exhaust pipe.......you may want to cut it out and splice in a straight section. It would be cheap and quick to do..

I would hate to see you go to the trouble of installing the four barrel setup with no change i performance.

You will need to install at least a 2.25" system to realize any real benefit of going to a bigger carb. I would do that first....I run a 2.5" system and it made a huge difference in performance and over all spunk. If you get headers later it's not that hard to hook up.
Author:  Rug_Trucker [ Sat Jan 14, 2012 7:36 am ]
Post subject: 
Really, IMO as a daily driver you are going to spend a bunch of time trying to tune a Qjet. Unless you can find a V-6 one. It might get you into the right neighbor hood quicker. Older Qjets should be easier to tune. Metering rods and jets is what you are going to need.

AFA your cat? Do you have to pass emissions in Tampa?

You can take a piece of rebar and a hammer to bust out the guts of the cat. The cat on my van gutted itself. I heard it rattling for a couple of months. I went to gut it when I changed mufflers. It was empty! :lol:
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