i have this 327 300 hp engine in my 64 impala,3.08 pumkin and a turbo glide all stock. The carb is a new rebuilt carter ,,this car is a pig on gas, i run run hi test in it.The car is gutless my 283 i had in it had more punch,and i never go over 60 i drive it like a baby carrage, she runs about 19 thow at that speed
Yes that is why the factory initiated going to EFI, abandoning carburetors and points fired ignitions, and single and even double overdrive transmissions in modern vehicles over the past thirty five years. Soon cars will be the size of Dixie cups made of aluminum and plastic to get to the required 45 miles to a gallon mandate. Aren't you glad you have a piece of old American iron.
Don't forget ignition timing and spark intensity has a lot to do with mileages as well. Getting the fuel air mix is half the battle getting it lit and burning completely while still in the chamber is the job of the ignition.
By the way all of my hot rods would be hard pressed to exceed 8 mpg, most were down around three miles to the gallon; with one race car I built requiring two gallons to the mile. All part of the cost of doing business in my opinion.
If mileage and performance is desired then a 6.0 or a 6.2 liter LS-3 or LQ-9 motor is what you want.
Are you saying you get 19mpg out of the 327? That sounds great to me
On my 64, I get 8-9 mpg on my 383 with 700r4 and 3.73 gear ratio. On the other hand it does get a lot of smiles per gallon with the acceleration ;D