305 v8 or 250 I6 for better mpg

[mnunn454]

Originally Posted by LEEVON

Sounds like a carb tuning issue. That thing has to be running rich to get 6-8mpg. I second the 2bbl and 3:08 gears and HEI, which should be good for at least 15mpg if not better. It won't be a powerhouse, but at least you'll still have the sound of the good ole' 350

I agree.

Before changing ring and pinions, or engines, or trannys, I'd start with the carb and HEI.

Regarding carb's:

A) Visit a chassis dyno and have them jet it for economy when cruising at highway speeds (NOT W.O.T. HP). Or,
B) Try carb tuning yourself by changing carb jets or needles and watching the plug colors (An O2 sensor in the exhaust pipe is a big plus in this regard). Or,
C) Replace the carb with a rebuilt Q-jet or Edelbrock #1405 or similar.

I'd think 12-13MPG isn't an unreasonable expectation for a V8/373 geared truck (once the air/fuel ratio is adjusted properly). The 50% reduction in fuel consumption will repay any hardware investment costs in short order.

To get 16MPG or more, you're likely going to have to drop to a 3.08 R&P or install an overdrive tranny (manual or automatic, you choose).

Upgrading to EFI and an overdrive tranny should net you over 18, but it's a lot of work and maybe cost to convert.

of course, all this assumes you don't have a gas guzzling cam, really low compression or the emergency brakes frozen up ('Been there. Done that. Got the T-shirt).