I was thinking along the same line as Vern. That 600 cfm carb seems a little too much for that engine, unless it is really warmed over. I have the Edelbrock 1406 600 cfm carb on my warmed over 400 (410) and I get around 10-12 mpg with it. I would look for a smaller 4V carb, or a 2V carb and intake...if you are looking for better mileage. My dad had one of the early Ford Broncos with a 302 in it and he says he always got really good mileage with it. Granted, tire size and gear ratios will play into the mileage, but your driving style has a lot to do with it as well.

 

Glue a 1" square of wood under the gas pedel near the top.
If that doesn't bring the milage try a 1.5 square block.

 

That would be 2 lights - highway - 2 lights.....at work....same thing on the return....i'll try to turn down the PSI from the fuel pump....can't turn my carb down anymore or it will choke out...i notice there was no difference in gas consumption when i switched out my original rearend with 4.10 gears to the 9" with 3.25 gears....like GNW said, maybe this is the cost of the hobby here - torque and power = burning fuel!!!

 

I have a 64 Econoline (C4 auto and 3.00 9" rear) that I put Ford 302 crate motor with 320HP in it. With a Holley 650cfm or an Eldebrock 500cfm carb it got 10-15 MPG no matter how careful I was with the gas pedal. After that I put an EFI system on it. Now I get 17-20 MPG.

 

I have a 289 with a holley 4 bbl and Edelbrock manifold in my 56. I get 16 on the highway with a c-4 and 9". Don't know the gears.

 

Maybe your speedometer is not accurate. You will never get an accurate m p g reading
until your speedometer is accurate. Good luck with your problem.

Gary

 

Good thought! My odometer only registers 0.9 for every mile driven. Check yours against a measured mile on an interstate somewhere...

 

Drive the Mazda daily and save the truck for fun and weekends. You can always find another rice burner. Not so easy with the old Ford trucks...

Later Man...

 

Hey Fat Fender,
Your Dad must have been one of the lucky ones. We had a '73 Rronco we bought new with a 302 and no matter what you did it only got about 10 MPG. It was a great vehicle to have and it was tough as nails if you didn't count being able to hear it rust on a quiet night. I used to joke about it and say the only way you could get better than 10 MPG was to push it of a cliff and calculate the mileagr it got on the way down. I had a 74 van with a 302 I also bought new and it was heavier than the Bronco and got better mileage. Same basic engine and tranny. Go figure... I later ahd a bearing spin and re did the van engine and put is a different cam, pistons, intake, went to a 4bbl, and headers and got about a 5 MPG improvement, not to mention way better performance.

When I rebuilt the van engine I used older higher compression pistons from a '68 302 and I always figured that had a lot to do with the higher mileage and better performance. In the '73-75 era they used a lot lower compression pistons which I think was due to trying to get the emmission standards up. They were true dogs around that time. I'm wondering what pistons are in the subject truck on this thread.

Later Man...

 

I just have to see leave my info on my truck and some input. I have a 302, 1406 edel, AOD, 3.23 gears, holley blue pump/regulator @ 5.5 p.s.i and a 16 gallon tank. I generally use a Garmin to watch my speed and use the odometer on there to check gas mileage. I have found that the garmin is accurate in late model vehicles so I am pretty sure of my mileage. From my numbers, I can go about 325 miles(with no ac on) to a 16 gallon tank and that is a little over 20mpg. Now my motor other than the 4bl is stock and will light up the tires and can run over 100mph but it is no drag racer by any means. The overdrive makes a big difference on a driver. I would also recommend adding Heat to your gas and keeping your fuel filters changed. Those little things can make a big difference. Also for the outback mustang tank users like me, make sure your pickup tube is in correctly or you will lose about 3 of those 16 gallons and sit on the side of the road thinking your fuel pump quit pumping.