Gas Mileage is poor

[BruthaMan]

Originally Posted by BruthaMan

My '72 gets about the same, on the highway.

4.11 gears with turbo 350 trans. At 50 MPG, I'm already at 2500 RPM.

It's a blast in-town, but on the HWY, she's a screamer! Hoping to add a 2004R down the road and/or find someone locally that wants to trade out axles for 3.73.

I really think keeping the RPM low is the key to good MPG on the HWY. I've been driving my truck from San Angelo to Lubbock for the past six months. It's about 200 miles each way. At 65-70, I typically get 10-11 MPG on the HWY.

Motors is tuned very well. I've spent a great deal of time on timing and tuning. Carb (Edelbrock 1406) is tuned well, recently rebuilt. One thing I did notice was, the plugs that were in the motor were .35 gap AC Delco. I swapped those out for Bosch Split V's gapped at .45 and it ran much better. Not necessarily MPG, but just idled better and was a snap to tune to the motor.

Coming back from Lubbock yesterday afternoon, I decided to just take it easy and keep the truck at 55 MPH. At 55 MPH, I'm at around 2750 RPM. I normally drive at 65. Gas mileage was considerably better. I normally have to stop in a town about 45 miles from home to refill with 1/8th tank left. This time, I was able to make it all the way back on one tank. 13.8 MPG.

Really need to get an overdrive to drop the RPM down and be able to drive at reasonable speeds. The only good thing about driving that slow is, I never have to pass anyone!