best size 2bbl carb or small 4 bbl for my 318?

IMO, disconnecting the secondary side of a 4 bbl. carb is a dumb move. If such a move was done, then I'd say install a 2bbl. carb.

SBKNUT is on it!

Heres the deal with 2 vs 4 bbl. carbs for starters. There rated differently. Different pressure drops. They flow differently at the sme drop. You want the 4bbl. and you want facts not some *** saying run the 2bbl. because it is smaller etc....
Garbage! Pure garbage.

For starters, sbknut is right. Your right foot will control 90% of your mileage at all times no matter what freakin carb is on top! BAR NONE!

1967dartgt's idea of a T-Q is an excellent idea but I left it out on purpose since you allready have a carb that is absoultley capable of getting everything you need. The bang vs the buck in swapping to a T-Q is not really there. The advantage of the smaller primaries for a greater velocity of air and fuel is a good thought and if tuned right, would show a marginal improvement.

Badart is right! Tune your carb and stop listening to people who have absoultely no idea what there talking about.
MOPEkiD-3 has said something very important and I have also been there and done that with exactly the same move he did. I moved from the 2bbl. BBD to the Carter 625 and found better milage. After I did that, I made many of the changes I mentioned above. These changes done to my car not just did the trick, but changed the car in everyway one would seek to do except consume more fuel.

The car was my 1979 Dodge Magnum with a 360. The car only lacked a moon roof or T tops , but had everything otherwise and a working coooold A/C system.

I went from a perfect emissions passing 10 MPG's Hwy. to 20 mpg's and still passed emissions and I feraking passed it better than the stock leanburn or the "FIX" Chrysler did for that disaterous computer, the "Orange box" did.

The following is ALL i did to the car.

"Trap Door" 1973 air cleaner with a K&N on top of a 625 Carter AFB on a stock iron intake with working EGR valve, dual exhaust of the manifolds into twin cats, H pipe, into $17 turbo mufflers to the tail pipe. A new viscous fan from MoPar and a MSD being triggered by a junk yard distributor that cost me a whopping $10.
Drive train was a 360/904/8-1/4 w/2.76 gears and 235/60/15's on all 4 corners.
The Magnum weighed in at 3780 lbs before gasoline and me or a spare tire.

IF I can get 20 mpg;s with a 360 in a car totaling over 4,000 lbs, why can't you or anyone do the same/similar or close with a 318 in an A body car?

Tune tune tune!
Do not use a 2bbl or disconnect the secondaries of a 4bbl. carb!:angry7: