Thank you in advance for any expertise you all can provide.

I have a 1978 Ford F-250 with four-wheel-drive. It sits on 35 inch tires and currently has a 351M. The engine has 150,000+ on it and burns a lot of oil. I have done an extensive tune-up (plugs, wires, cap/rotor, coil, timing, carb rebuild/tuned, etc.) and still am getting around 8 miles per gallon.

I am toying with the idea of putting a 300 into the truck, because I have fallen in love with the engine after reading what everyone has to say about it. I don't want anything fast; I just want a durable, slow-turning engine that is easy to work on and very reliable. Fuel economy (at least matching what I'm getting now) would be a nice bonus.

After talking with some of my good friends, no one seems to think my idea is a good one. They all tell me the engine won't pull my truck and that I will probably get worse gas mileage. One friend even told me I would wear out the engine prematurely pulling a 3/4 ton truck.

I guess I really have two questions for you all:

1. Wasn't the 300 I6 the baseline engine from the factory for F-250s? I know it won't be quick, but it'll pull my truck won't it?

2. What do you guys think about the mileage issue? Am I crazy to hope to 12-15 mpg with a 300 in my truck's configuration?

Once again, thank you for your help.

 

I'm pretty sure you'll have plenty of power with the 300. especially if you already have the expectations of a "slow turning, durable, reliable" engine. you could also add a 4bbl and open the exhaust up while you're at it, to get even more power.

 

The 300-6 will work fine. I'd say go for it. Fuel mileage depends on what gear ratios you have in the trany and the differential.

 

300's were put in even the bigger trucks, so I wouldn't worry about it wearing out prematurely. Besides, there's not much weight difference between yours and a half ton. Expect to get a donor truck with the 6 in it for parts swapping as it's not a direct bolt-in.

 

I have a 74 F250 with an 80 300, 4 spd, 4.10s and 36s. I am really happy with the setup. I "downgraded" from the holley 390 to a motorcraft 2150 off a 77 302, and I am getting about 14 with the setup listed. That is gps mileage, not odometer. I say go for it, but don't run the 1 bbl carb. At least upgrade to a better intake, 2bbl and dual exhaust.

 

No it won't hold up in a 3/4 ton 4x4... They were only used in: irrigation pumps, wood chippers, tractors, school buses, Grumman delivery trucks, dump trucks, forklifts. Yeah it won't hold up... my a$$...JK! You will be more than happy with it in your pickup truck if you are looking for a low revving torque monster. They are a super reliable and durable and long living engine you can depend on. It sounds like your buddies just don't like inline six cylinder engines... screw em drop on in your truck, you won't regret it. You will have to change your tranny bellhousing (if it's a manual) or go to a small block Ford/ 300 six automatic transmission. I recommend running a 4 speed creeper box with a 300 (NP435 or BW T18 or BW T19) the 300s don't tent to perform as well with an automatic. I have a 300/ NP435 combo in my 84 F150 4x4 with 4.10s, 33" mudders, locked rear, lsd front... she will pull anything you hook to her! BTW 300s were the base engine in the F-series pickups from the light duty F100 to the F350... the 302 V8 was only available up to F250s, if that tells you something about the 300!

 

The B code 300 six was avalible in a 78 F250 4x4 and they held up great like every thing with a 300, I have only seen one of these truck and it was a very well travled county plow truck that i should have bought but didn't have the money now i have a 79 F250 4x4 with a 400 that isn't nearly as powerful as the 300 in my old 82 F100 or the one in my 89 Bronco with 273,000 miles. A 300 six will stand up to twice the punishment a 351M can for six times as long.
-johnboy

 

So, abboq, what did you decide? Either way, post pics of your rig.

 

The 300 will do fine in that truck, but you've got some work to do to get it in there. You might be ahead to find a 400 in good condition and drop it in.

 

That is a good point, your truck is already set up for a 351m/400 you might as well go with a 400. They too are a big bore big stroke motor that makes good power at low rpms. They actually have a little more power on the top side of the powerband than the 300, the downside is you will be lucky to get 10 mpg out of one.

 

A 400 is basically a 300 with two more cylinders in a V formation. You could build one into a very torquey and efficient engine. It wouldn't surprise me if you could build one that got 14-15 mpg on the highway. The biggest problem with the 400 is that it was developed at the wrong time. The emissions regulations killed it before it was born.

 

Thank you all very much for your insight. I have decided to begin looking for a 300. I currently have the four-speed manual and want to stay with a manual, so I figure I will need to find that donor truck as advised. I appreciate the suggestion of the 400. The idea is tempting, but I just can't wait to see a straight-six sitting underneath my hood. I've fallen in love with the elegant simplicity and over-engineering of the design.

I will look for my digital camera and get some pictures of my truck up here as suggested.

Again, thank you all for your advice!

 

I dropped a 300 in my 79 bronco, so I know all about yer 351m woes. A 4 speed manual will be easier, as all you need is a bellhousing. (I used a C6, but that'll get swapped out next year) Good luck.

 

The swap with a 4 speed will be pretty easy then, all you need is a manual trans bellhousing for a 300, 302, or 351w (they all used the same bellhousing) and the motor mount towers and mounts for a 300. I don't think the V8 radiator will work I could be wrong, I know the V8 and inline six rads were different in the 80s trucks ( coolant inlet and outlets were on opposite sides) not sure on the 70s trucks. Either way you go (300 or 400) will be a good choice, both motors were low rpm torquey work horses.

 

I would say try and keep the rad. I think the 400 rads were bigger. After you get the 300 swapped in, go and try to find generic hose at the parts store. I have a mopar rad in my truck, and I just looked at the hoses until I found some that would work for my app. The only thing I am not sure about is the bottom of the 400 rad. The 300 is a pass side hookup to the radiator.