Ford 390 build for F350

Hi Gentlemen,

I've studied this Club HOTROD site and believe there are some very savvy engine builders here, including a professional or two. Here's my question: what are your thoughts for my building a good performing Ford truck 390 that will balance fuel economy with performance? The F350 is a low mile truck with the following: 12' Napheide flatbed, dual wheels, Dana 70--4.10, C6 transmission, stock everything. The 390 runs great, even with the horrible FE exhaust manifolds and Motorcraft 2 bbl. It flies down the highway with ease but won't pass a gas station. I don't drive it with a heavy foot most of the time. We're paying about $4.60 / gallon for regular gas in Alaska. My plan is to throw the FE exhaust manifolds away and replace them with Sanderson headers. I'm not sure about the rest. If I could achieve 13 or 14 mpg with a more modern cam and Edelbrock Performer or Performer RPM intake manifold, I'll consider spending money on an engine upgrade. I'd like to choose a reliable and efficient carburetor. Any thoughts on a good efficient 4 bbl carb for this application? I've installed a GM HEI style distributor and that is a good improvement over the worn out points distributor. With this 6,600 lb truck, I'm seeing 8 to 10 mpg now. Another possibility for a mod is to stuff the 403 Olds I have hanging on an engine stand into the F350 with a 400TH bolted to it. I realize many folks laugh at the 403 Olds but its a mild performance build and it made my old Trans Am fly down the highway with a steady 16 mpg. In dad's motor home, a 403 Olds got a consistent 10 mpg. They are good torque motors and perhaps have combustion chamber and manifolding design to achieve a bit better fuel economy than a similar cubic inch Ford FE. Do any of you guys know that to be a false assumption? If any of you engine builders with extensive experience have any sound advice, please let me know and don't be afraid you'll offend me--that's not possible. Engine building for a very specific application isn't exactly an exact science and theories with no experience to back them up have little appeal to me. Thanks for any thoughts, friends!!
--jimmyjack

If you only want to improve mileage, change out the final drive ratio to something more favorable. Say 3.50 to 3.70's...

Helping the engine breathe can be a dual edge sword in a lot of cases, helping the flow through the heads also can increase consumption and FE's have always been a hungry motor.

Using the "Other" motor I find replusive.. If you were going to build/rebuild the FE, find a 428 crank and add the edelbrock top end package, heads / cam / intake / carb... but you're gas consumption won't be going down as you'll need new tires more quickly also!!

And welcome to the club, nice to see you here!

Welcome to CHR, good having you with us! About all I've ever gotten out of an FE for mileage was in the 12-14 mpg range. Mileage just was not a consideration when these engines were designed!!! Back when the F-250's with an FE engines were the truck to be towing with we had a few different combinations but that was about the best we got----and if you left late for the track and had to hurry, that number would drop to the 8-10 mpg range! Another consideration would be to build the engine for torque and mileage, then put in a Gearvendor's Overdrive unit to scrub off a lot of RPM!

If the truck's a keeper and towing power along with good mileage is your criteria, I'd suggest save up some coin and find a take-out 7.3L Ford Diesel with a 5 speed behind it! My current toter has that combination and exceeds your 13-14 mpg by a considerable amount, with the trailer hooked up and the AC on! I'm sure such a take-out diesel in your "neighborhood" would be quite expensive, but still probably worth the investment if the truck is a keeper!!!!!

Thanks for the thoughts, friends! I agree that a 7.3 would be a good choice for a re-power. The 403 Olds would require some work to replace the 390 and not be as good a choice as a 7.3.