I was reading a post about putting a 4.6L Mod in a F250, I am not interested in this at all, I have the 460 and would like to keep it. I do have the possibility of getting an early 90's (92-93?) F250 with a 460 and a bad trans very cheap. The body is good and I might use the parts to update the look of my truck if I get it.
Anyway, because it would have a 460 in it I thought it would be nice to do a rebuild with MPG in mind.
Now, I live in the real world and know that a 460 is always going to love the fuel and I will never see 25 MPG (or even close), but I did read in this post by cadukle that he was getting mid teens:
https://www.ford-trucks.com/forums/1...60-to-mod.html
"My 460 puts out about 425 HP/550 ft/lbs. I would wager that if I put the truck back to stock height it would get about 16 MPG, maybe more with the overdrive. If I built and tuned the engine for peak MPG I could probably squeeze about 20 MPG out of a 460 based engine in an '80-'96 truck. That's about as good as you're gonna get without going to a diesel."

So, what would I need to do to build a core engine for MPG? If I could really see mid teens out of a F250 4x4 with a 460 I would be able to use it as a daily driver and save the money on insurance.
Is this realistic or dream land?

 

You can hit mid teens on the highway with the right combo but in stop and go traffic you'll be lucky to see 10.

 

Sorry for not replying sooner. It's been a busy week so I wanted to have some time to give a proper outline for this build. It's not happening, so I'll give a quick rundown of a decent MPG build before I call it a night. With a build along these lines you should be in mid-high teens for highway MPG in a stock '80-'97. Basically getting the MPG you'd get from a stock small block but with the extra power of a 460.

For a MPG 460 build in an '80-'97 there are a few factors. Name what it's going into and the intended use. to get high teens or even 20 MPG we're talking a stock height truck not intended for heavy towing.

Assuming we're starting with a '80s truck 460 with D3VE or E6TE heads I would do build along these lines.

KB137 pistons
Zero deck block (you'll be shaving about .040")
D3VE/E6TE heads ported intake/exhaust (port as per Scotty J)
Polish chambers
Singh grooves in chambers
Lunati 61601
Straight up double roller
Edelbrock Performer intake port matched to heads
Holley 4150 750 CFM vac sec, preferably annular boosters on primaries

Aside from that you'll want a ZF5 trans with 3.55:1 axle ratio, maybe less gear depending on intended use. The idea here is keep RPM as low as possible. ZF5 with 3.55:1 will keep you around 2000 RPM at 65-70 MPH. You want to be between 1500-2000 RPM at cruising speed to stay in the torque curve but not spin more RPM than you need to.

A lot of your MPG will come from timing and jetting.You want as much timing as possible. More timing means less fuel required at a given RPM and load. The chambers on these iron heads love timing. Ideally you'll be shooting for ballpark of 16* inital and 38* full mechanical. Available fuel may not permit this. With those pistons and cam duration with the wide LSA it'll be wanting high octane, like 94-96 to run best. This is a compromise to use off the shelf parts and get the compression we want. This is why we polish the chambers and do singh grooves, to make it take this dynamic compression on lower octane. I'm assuming you can get at least 93 octane where you live. 92 not that big a deal, 91 could be a problem requiring a different cam or other changes.

You'll also want lots of vacuum advance. For MPG I recommend using manifold vacuum on your advance. Give it as much as it'll take and not ping on the highway. Manifold works well for MPG tunes as it'll back off under load. The more you open the throttle the less vacuum advance it gets. Once you're up to speed just cracking the throttle you may have total advance well over 40*.

On the carb you'll jet lean. As lean as you can without a lean surge. Then go 2 sizes rich of wherever you get a lean surge. Once you get that jetting you can play with secondary jetting and spring rates to get best performance. You may need to enlarge the PVCR's to get a rich enough mixture when you drop the hammer. Go small increments if you do, as in a few thousandths at a time.

A lot of a MPG built is fine tuning. It'll take some tweaking to get that last 1-2 MPG out of your build.

So there you have it... With more specifics we could do a better outline. Power goals, MPG goals, specific truck, etc. At the end of the day it amounts to keeping a low RPM, make good torque at that RPM, high compression, keep mixture as lean as possible, and as much timing as it'll take.