BBC and gas mileage

[80superbu]

For my 67 SS396 Chevelle project I was planning to run a turbo'd LS1 (which I have already). I'm having other thoughts. I'd like to put a big block in it since it is an original 396 car. A big motor under the hood looks good. With the LS1 I was going to run 6 speed. If I do the BBC it will be a 4 speed so I can reuse the original 4 speed console.
The one thing that has kept me from this is the gas mileage. Is it possible to have a BBC and get around 20mpg.
Most likely will be something other than a carb.

Anyone here running a BBC w/4 speed? what kind of mileage you getting?

Thanks

[Vegas69]

Sorry but their is no way unless you ***** foot it on the freeway. Fuel injection would help some.

[RatMalibu]

my car with a 489 BBC 750 holley th-700-R4 and 3.42's got 15mpg at 80mph average.....the carb is too small and not really even close to tuned correctly...I put a T-56 in it and plan to EFI it when the $$$ allows and I'm shooting for 20

the key to your combo will be OD.....maybe a 2.50 or so rear gear? lol

[Bandit]

On a 1,000 mile trip, I documented an average of about 17 mpg with my BBC 402 (fairly mild cam, 750 Holley carb) and 3:08 rear gears with a TH350 trans--NO overdrive. I feel confident it would have pulled 20 mpg easy with the TKO trans I have now.

[justanova]

my dads 70 caprice with a mild 402/th350 and 2.56 gears got an average of 18mpg on a road trip from iowa to arizona driving 75-85 the whole way. Now he has a 700r4 and just re-geared to 3.55, no info on mileage yet, he hasn't got it out for the spring yet.

eng. combo:
stock oval port heads, performer intake, crane powermax 290h cam, and a "jet" reworked q-jet.

if you could put the 6-speed behind the big block and put 3.42-3.73 gears it shouldn't be a problem. i believe there are diff. shifter housings available to locate the shifter so you can still use the factory counsole