i have a 305 chevy small block with a 650 cfm edelbrock carb with edelbrock manifold...i was thinking about selling manifold, carb, and air filter to buy a holley duel carb manifold and a couple of smaller carbs .i know my gas mileage isnt going to be all that great but it already sucks. just wondering how much more torque/hp i would be pumping out and if i will be getting more/less miles to the gallon.

 

You will eat up the extra gas. The HP/TQ difference will be nothing to write home about. You will also probably loose most of your low-speed torque and driveability. Then there is the simple fact that EMISSION's Test in TEXAS are a fact of life for everyone here in the near future. I am already under the new laws, it is just a matter of time before it goes bigger. My suggestion is to get an Edelbrock Quadrajet 1904 and a Performer RPM Spreadbore intake as well as a good distributer or a recuve on your existing one.

 

for an N/A 305 it would be too much

 

The secret to a dualquad setup for a 305 is small carbs.
Edelbrock just released a new RPM Air_gap dual quad hirise manifold for SB's and SB's with vortec heads.

Cool Cool Cool

 

a pic

 

Dual carbs will get you no more power than a single larger carb, but you'll have a whole lot more tuning headaches.