15 years ago, my dad and I repainted my F-250, and put in a rebuilt 400 and C6. My dad bought the truck new, so it's like a member of the family.

He officially handed it over to me about 5 years ago, but I rarely drive it due to it getting about 8 MPG and no AC. I've always kicked myself for not putting an AOD or E4OD in it when we had everything out.

It's got an Edelbrock performer carb on it that I have to tinker with every few months. I have to run non ethanol gas plus octane boost to keep the carb from gumming up, and the choke sticks all the time. I need something more consistent.

I've gotten to a point where I'd like to breath some life, reliability, and comfort back into "old blue", but I don't have a big budget. Transplanting a 5.0 seems quite extensive and expensive. Putting in an overdrive tranny seems pretty doable, and I am also interested in a EFI kit. Any suggestions about things I can do for a good value are appreciated.

 

Sniper EFI or FI Tech are currently the lowest-buck EFI systems.

Headers and dual exhaust for better efficiency.

Adjust your driving style - learn to "hypermile". Remove unnecessary weight. Eliminate rolling resistance.

2WD? I would think you could better than 8 MPG.

 

I have a 78 150 short bed 4x4, 400 with 6c and get 10mpgs but I have Fitech too.

 

Already have headers and dual exhaust. It's a 2wd.

The low gear Dana rear end surely doesn't help matters. The truck has never been a good coaster. It's slows quickly on its own. It's always been that way, so I don't think there's a mechanical problem.

Heliguy - what mpg did you get before the conversion?

 

A straight up timing set helps those M engines too. Another wheezy thing Ford did to meet emissions, retard the valve timing.
I've been in hundreds of threads about fuel consumption and there are as many opinions. But some engines just don't run as good, or freely as others. I attribute it to core shift when they cast engine parts. Many moons ago I raced dirt roundy round and we couldn't do any port or polish work. We would take 10 identical sets of heads to get flowed. 2 or three sets would be just horrible, one or two sets would be real good and the rest somewhere in the middle.
C6 trannys are a horrible parasite of power and economy. I've read they can rob as much as 60 horsepower, or more.

 

I want to say 8 or so. It was in horrible shape and I didnt drive it much before the frame off...

 

4.10 rear gears? I can relate.

Limit it to 60 mph max on the highway. The aero of these rigs are horrible and requires an exponential increase in fuel consumption over the increase in speed or maintenance of velocity

Coast in anticipation of stop signs and traffic signals.

Easy on the acceleration. Rabbit starts kill MPGs.

Repack the wheel bearings and maybe switch to synthetic lubricants.

Tune, tune, tune. Get yourself a vacuum gauge and understand how to use it to be efficient...in other words, it's like a shift light and throttle position sensor all in one.

 

That's about what mine was getting when I bought it a few months ago.. 78 F-250 4X4, MT and 4.10 gears.. Went through and did general maintenance tune up, wires plugs oil and filters.. Found a huge vacuum leak, one front caliper was dragging and the distributor was not advancing, fixed those and now 13mpg highway and 9.5 towing a 2700# race car spares and tools on an open trailer. Towing, that's as good as my 07 Nissan Titan gets.. The Ford does not get there as fast though

 

Within the past year, I have added a two-wire distributor, changed spark plugs, and rehabbed one of the fuel tanks (just bypassed the other for now). That helped a bit, but I'm sure a good tune could make it better.

I can definitely say that I'm not the best at tuning. I had the exact same 750cfm carb on a street rod and got a lot of "practice" trying to dial them in. I would get them running great for a couple weeks, and any change in temp would make it trash. I'm just sick of having to fool with it on a work truck. The EFI sounds good, but over $1K for a kit might be too much for me. At this point, a reliable daily driver carb that I could run premium standard ethanol gas in would make me happy.

 

One more thing to add, I was skeptical of the stock carb but all the research I did said it was perfectly sized and calibrated for the engine and truck. After the tune up and removing the EGR plate the truck started and idled fine with no flat spots or hesitation so I'm running the stock 2 barrel. I just cleaned the crud off it and replaced the fuel filter.

 

That stock carter carb was the business. The truck would crank as good as any EFI vehicle back in the day. I still have it and the old 400. The current engine is more souped up, and I assumed the stock carb would be too restrictive.

I even tried a 600 cfm carb on the truck for a while. The mileage didn't improve, and it felt restricted. Again, it could be on me for not getting the most out of it.

 

Hah, was just about to say the 750 carb might be your problem, that's pretty big for an otherwise-stockish motor.

On a 2wd, it's fairly reasonable to gear-up, junkyard complete rears around here are pretty cheap. But outside of that, a good intake manifold and one of the drop-on, self-learning EFI setups is probably the best way to clean one up, and a timing set eventually.

My '78 F-250 4x4 has been getting around 12-13 hwy, as long as I keep it under 75, with 3.55's. It's 100% stock, and nicely tuned (not by me).