Hi folks,

My dad recently passed away and I inherited his camper rig, a 97 F-250 HD 4x4 with the 351w and a 4.10 rear end. He used this truck to haul around his Alaskan pop-up truck bed camper. The truck's got 103,000 miles and has been well maintained. The camper weighs approximately 1900 lbs and probably had another couple hundred pounds of gear in it, and just me driving (200 lbs).

It hadn't been driven in months, according to my mom, and I do remember that truck always had issues with pinging on heavy throttle uphills unless we used at least 88 octane gas. Both tanks were about 3/4 full with unknown grade gas; I topped them both off with 91 octane to freshen things up.

I drove it home in 40 mph gusts and had a hard time even maintaining 60 mph on uphills. It's 120 miles from my mom's house to home and I burned more than 3/4 of a tank getting there. About 8 MPG.

I was really unimpressed both with the power and fuel economy.

Now, I'm wondering if that was because of old gas, or if the 351w is really just a dog. I don't remember it being this bad when I drove it on a road trip in 2010, but that was before I had driven several IDI diesel trucks, so I may just not have had a basis for comparison back then.

I'm trying to figure out what to do. I'm keeping the camper regardless, but I'm thinking maybe about moving to a 460 or a diesel (7.3 IDI turbo).

The 351w and the 460, under loaded or towing conditions, seem to get similar fuel economy, and the 460 would be a heck of a lot more powerful. Similarly, a diesel would get significantly better economy and fall about halfway between the 351 and 460, power wise.

460s are cheap because they get such terrible fuel economy, but this truck will be primarily for the camper (and occasionally hauling stuff to the dump, etc). Most of the time it's going to sit.

What would you do in my situation? This truck is beautiful and I've got a standing offer of $6000 for it, which would buy me a nice 460 or IDI truck and have money to spare.

 

A 460 will get 8-10 mpg everywhere all the time even when the truck is completely empty while the 5.8 will get into the mid teens and there is lots of untapped potential in an all stock motor for both power and milage increases. Swapping in a bigblock or diesel is a complete powertrain swap in case you're not aware, the small block trans is not compatable and that means you could also lose overdrive if you don't put another E4OD back and this will completely kill any milage gains you might see wiith the diesel for example.

 

Well, this truck is almost never going to be empty, so that's a nonissue. From what I've observed and from what my dad told me in the past, this truck always got 8-11 mpg with the camper on. So if a 460 got the same and had a lot more power, that's a net gain in my book.

Diesel ... seems like the best of both worlds, but they're dang hard to find around here in any decent condition.

 

Yeah it'll never get great milage with a camper in the back but the 5.8 can be tweaked to pretty close to stock 460 power levels which will save you a ton of work.

 

Is it possible to do that tweaking without significantly affecting reliability or lifespan?

And what sort of cost are we talking here?

 

Oh yeah, the big thing is to get some longtubes on there to replace the stock manifolds and then put a free flowing single exhaust system behind them, and then add 1.7 roller rockers to put the motor into the 250-260hp/375Tq range. Swap on GT40 heads for a decent HP gain but they won't make any more torque than the stock heads.

 

Hrm, I'm also wondering if I can do all this and still have the truck pass emissions. I don't need to worry about it right now, but in the future I may.

 

I used to carry a 1200# pop-up camper (the one in my avatar picture) while towing a 3500# Jeep and carrying my family of 4 with a weeks worth of gear with a '95 F-150 with a 351W, E4OD, 3.54 gears an 33" tires. I'd get about 7 mpg like that, but I was always OK with the performance. With the tall gears and tall tires I couldn't pull hills in overdrive, but I could usually hold 60 in 3rd gear. So unless your hills are a lot steeper than the ones I'm remembering it seems like your 351 ought to do better than what you're seeing.

On the other hand, if it was me and I knew I'd never be empty, I'd probably sell it and get a diesel. My '02 7.3L would get 11-12 mpg carrying that camper and towing a heavier Bronco. And I could win drag races while doing it (well, a few drag races).

 

Sorry for your loss.

Just my .2cents but if it's a toy that will be sitting for most of the time, why put a lot of money into it especially an engine swap? I would follow Conanski's recommendations and if he gives the green light, look into doing the 6 liter tune. My truck has a manual trans but I can maintain 65mph on grades with my camper and pulling a trailer with two quads. The steep stuff will make me drop to 45mph. But, my truck has issues that I'm still working on.

 

If fuel economy isn't an issue for you, get a 460 or tuned 351.

If your a cheap **** and want best economy, and long life with a hard worked engine, get a Diesel!


My 1990 F250 4x4 5 speed 7.3L non turbo Diesel got 12-14mpg in the mid '90's with this thing in the box!

 

dear lord that's a huge camper. Must have sucked driving in high winds.

 

any thought that the old gas is going bad and that is the reason for the bad mpg?

 

That camper is a pop-up type unit. My 1997 F250HD in my sig line lost exactly one mpg with a 10 ft Alaskan cabover in the bed.

Too bad it was just a loan from a friend. That hard-side camper is very managable in a crosswind.

 

As long as you put a cat on it yes, and if you don't have visual inspections you can also delete the whole air injection system since it does nothing once the motor is at operating temp anyway.

 

Thanks, man.

Oh, I wasn't thinking of doing an engine swap (and believe me, if I were seriously considering that, it would be to a first-gen Powerstroke). I was just thinking of selling this truck and getting a more suitable one.