78 supercab F-250 4x4 that's being converted to 1 ton. Soon to have 4:56 gears, currently at like, 4:10. Im not thrilled with the factory 351M: Its big block thirsty and grossly underpowered in the torque dept. I don't wanna dump money into building up a V8 that's only going to get 10 MPG when im done.

Ive seen 240s and 300s in 1/2 ton pickups run forever and pull down respectable mileage.

BUT WOULD YOU USE AN I-6 IN A ONE TON DUMP THAT HAULS STONE, PLOWS SNOW AND PULLS A HEAVY TRAILER?

Im trying to avoid the "gotta have a 460" mentality, I want a little fuel mileage, longevity and ease of maintenance. I need LOTS of torque way down low. Im prepared to BUILD a 300 6......... but only if its up to the task of extreme abuse daily.

Thoughts/opinions?

 

Ford used the 300 in their dump trucks. Nothing more needs to be said.

 

Yes, so was the 351M/400, and Im not too impressed with that.

Will it hold up to being pegged to redline all day when plowing or have enough low end grunt to haul a ton of manure while pulling a trailer?

 

The 300 was used for 41 years. It's reliability is about as good as you'll ever get. It's one of those engines you'll hear guys joke about how they went out on a weekend with their buds and tried to blow it up, only to fail. Will it hold up? I'd say yes, but I can't guarantee it. What I will say though is that if there is any engine that will be able to handle that job, it's the 300. It's always been a torquey towing and hauling engine. That's what it was designed for. Ever see a Tug at an airport? That's got a 300 in it.

If I had extra money and time though, I'd throw in a diesel.

 

I had several Fords from the 70s with 400s, never was impressed with their (lack of) performance. ~Bill

 

I don't think anyone ever has been impressed by the 400. It's great for being pulled out and turned into a table though!

 

The 300 was used for decades for lots of applications where it ran all day long at high RPM. Almost all UPS trucks had them for many years. Wood chippers, ski lifts, irrigation pumps, etc. etc. It's not going to be fast, but it's made to work.

 

IIRC the 351M and 300 have the exact same peak torque at the same rpm. I don't think even a built 300 would be stronger than a built 400 - i.e. your current block and 400 crank/rods/pistons.

Or build a 429. A 1 ton cries out for a diesel, mostly.

 

The 300 will provide plenty of power and torque. You can't go wrong.

 

I have seen 6 bangers in 1 1/2 ton trucks. I drove one back in my air force days

 

Your 351M suffers many indignities, low compression being the primary and a lousy cam being a close second.

Put an RV type cam in it. You may have to change the springs with a cam that actually opens the valves, but that's not a big deal compared to an engine swap.

Check out the first one up here, the H-192:

http://www.cranecams.com/230-233.pdf

More propaganda about the 351m/400, including the cam thing.

M-Block 351M/400 Performance

Anyway, that should give you a bump in torque and HP even using the stock 2bbl and exhaust manifolds. And that bump will be more than a stock carb'd 300.

As far as durability, unless you get the HD 300, the 300 is going to suffer just a much as the 351m and probably last no longer.

As for MPGs, a 300 with those gears and that load is going to drink fuel with the best of them.

JMO, but I would not fool around with an engine swap, especially to an engine that makes about the same power as your stocker.

You can cam that 351m into a little better performer and run it 'till you can swap over to a bigger oil burner for this kind of work.

Good luck with it.

 

I rebuilt my 400M with an RV cam. I had awesome power. I had awful gas mileage. My neighbor had a 300 six and his wife drove the family 351. The guy was always complaining about the 351's gas mileage. just sayin'

 

Like several have mentioned before...the 300 was built to work. Its easily maintained, easy to tear down and build, and will outlast most anything running. There is a reason it lasted from 1965 thru 1996. Lets be honest, mileage simply isnt a primary variable when hauling huge loads like described above unless you apply forced induction and/or diesel power. However, the 4.9L will keep going when most will leave you stranded. Seven main bearings, long stroke with inherent low end torque, and as long as you're not building a hot rod...fair mpg with careful maintenance and a good tune. Cant go wrong with an inline for a work truck man. Hope you're as happy with yours as we are if/when you do the swap.