I was talking to my buddy yesterday about my gtx and how the car runs great but eats gas like it is going out of style. He asked why not disconnect one carburator when you are just cruising around for better mileage and I said I am not sure that it can be done but would ask the question? Can this be done without any ill effects?

If you disconnect one carb you will run lean on one end of the block. A single carb tunnel ram would be a good route but not much for improvement. For fuel economy switch to a dual plane intake and carb that will match up with your set-up.

Does he have progressive linkage on the carbs ? ... the REAR carb should feed the whole motor on a lite-cruise just fine.

EATS gas ? .. then the jetting is way off on the carbs.

What carbs???
something is not right

My gtx was the car in question and my carbs are a bit rich and it wont give me no more than 10 mpg on the highway. Again the question was asked to me and I am asking here on the board. As was said I would think a lean condition from the cylinders that the disconnected carb was feeding would be an issue.

Can't you just block the secondaries of both carbs so the you are still using both carbs but only the primaries?

With stock linkage it should just be running on the rear carb at cruise speed, 10mpg is about right as it takes a lot of fuel to keep those ports happy.

A local guy I know with a 70 GTX gets about 10-12 out his at best, it's around 450" 12-1 comp, solid roller, MP aluminum heads, stock manifold & 2-600 edelbrocks- rear carb has an electric choke, 727 w/2,700 stall & 3.54's. 10-12 is straight hwy w/29" street tires, if he has 28" drag radials on it drops and if he romps it his avg mpg goes to 4-5. It's not built for economy he just tracks MPG since it will go thru a tank of gas in 2 hrs cruising around.

If it were me I would get a Lm1 and weld bungs in the exhaust for 02's and tune the carbs.

If it's setup correctly with progressive linkage you should not be operating the front carb at cruise speed at all, only the rear carb. All 4 throttle plates on the front carb should stay shut at cruise. When you nail it you want them all open and that is what the progressive linkage is for. On a dual carb setup you are tuning for mileage, you probably don't even want the idle circuit to operate on the front carb. You just want to run the whole show off the back carb until you get on the throttle a little...

Trust me my carbs are set up correctly and they are one to one.

If you're running an in-line intake and the linkage is set up like this, it will be progressive and the front carb will only function when you put your foot in it. You can remove the link and leave the front carb off completely.

Herb: Are you running a Stage V intake? The stock intake obviously works with the progressive linkage but the Stage V is a single plane design.

Sheldon

Listen up people.....an ENGINE needs a certain A/F ratio to run properly. It doesn't care how it gets it. Dual Quads set up properly are just as fuel efficent as a 2brl carb, which can be just as fuel efficent as fuel injection.

An A/F meter (LM-1) is the best way to tune things and get the ratio correct for all driving situations (cruise, idle, accel pumps, wot,.....)

TO answer your question, OF course you can disconnect one carb, and re-adjust the IDLE SPEED SCREW. You (theoretically) should not need to adjust the idle mix screw. But that's a bid too perfect, as you will start getting into the transition circuit, the more you open the blades up.

But you are just masking the problem here......Get the Carbs setup and you'll be just as efficent as a 2brl!

Oh yeah,,...and Here is how my car is setup and I get excellent gas mileage for the power it produces:

Idle: 14.5-14.8
Cruising: 13.8-15.0
WOT: 12.8-13.1

i have the stage V also, with 2 650 eddy's. i also get lousy milage, but with a 472 running 1 to 1 on the carbs, i'm not sure i can expect much else.

i have talked with tim banning at FHO, and with the guy, (can't remember his name), at stage V who makes the manifold and they both say run it 1:1. now, i never did ask about mileage, so maybe that is another issue.

i assume though that if you could get better mileage, the same power, and not run the front part of the engine lean, they would have said so. would be worth double checking and asking that.

herb, do you have your vacuum advance set up? that would obviously help on the highway. although i have never checked actual mileage, i did seem to notice a difference when i got mine coming it at the right time.

oh, and stage V finally has a real web site after all these years!

www.stagev.com

and for some really heavy duty stuff, check out the 308 on the specials page

I wish there were some prices listed. I have been thinking of getting a Hemi, but remember reading about these heads years ago. How much did a complete set of heads run you guys?