I've had some one ton trucks and vans over the years that had the 300 6cyl engines in them... and I LOVE them because the 90% of the time I'm NOT hauling something, they are not terrible fuel burners to get around (or to go long distances to look at something for sale.

Here's my question: If I were to build my own 1980's to 1990's F350 or F450 type rollback truck with an aluminum bed, if I don't mind the extra shifting, slow starts, and not pushing it on the highway, is it reasonable to build my every-day, long distance truck with a 6cyl gas engine in it? I'd only haul something on occasion, and wouldn't need to push it when I did. Decent mileage is EVERYTHING to me, and a diesel isn't an option (other reasons). I'd even add a GearVendor's step up to the 5 speed, but the 6cyl question is the part I'm hoping someone else with experience here can answer.

Thank you in advance!

 

It takes the same amount of energy to move the truck, so you will burn about as much gas, and you will burn it slow..... I had an E150 with the six, and it was a fine mover, but it moved slow.

 

Yes it will work, you won't win any races and may have to downshift more often on hills but it will tug your rig around. When getting going and moving around the 300 gets its torque low and at the low speeds it will have as much as any of the gas V8's of the same years, highway speeds would be a different story.

 

Couple nice things about the 300 I-6's....the suckers run forever and they're relatively easy to keep in service. Depending on your gearing, a gear vendor may or may not help. These engines have a power band like a diesel...all down low.

For fuel economy, the I-6 will probably perform better vs larger V-8's in around town driving where the V-8 will use more gas just sitting. When driving freeway speed, the mpg of a larger V-8 may be a little closer to the I-6 due to the increase in power demand to maintain freeway speed. At the worst, the I-6 should out do the V-8's (351 cubes and up) by at least 2-3 mpg on freeway.

Won't tow much weight at freeway speeds but should be able to handle a couple ton payload in an F350. Will help a little if the truck is 2wd with a stick and not 4wd with an auto.

 

Yes! Exactly. 2wd and a stick shift on the floor- I'm more interested to make the 6cyl work than to have a ton of power. Mostly hauling small, light cars from VW to carbon fiber exotics. MPG is my main concern.

 

This is what I'm looking to build out...something like the truck below, a rollback that has a 300 6cyl w/5spd trans, in a F350. I have never seen one before, and before I start to put one together, I'm just wondering if there is a reason I never see one with a 6cyl that I don't know about.

 

Ford stopped making the I-6 in 1996. I heard the reason was Ford couldn't (or didn't want to) get the emissions low enough for EPA rules. My guess is they also couldn't get enough power out of the I-6 to satisfy customers. The I-6 was introduced long before folks wanted to tow huge trailers at 70 mph with their 4wd king cab weighing in at 8,000 lbs empty.

The I-6 won't likely accelerate the truck you mentioned in a way that meets today's customer expectations. I've seen sites that advertise power upgrades for the I-6 but never really looked into it. I'm guessing you could get a little more cam or some head work for some more pep end not hurt fuel economy much.

 

Yeah, that makes sense to me- it's definitely a small group of people who'd want such a motor in something like this... That's why I figured I'd make my own, I dont mind slow acceleration and limited power. If anyone else out there knows of a reason I shouldn't, let me know... thanks!

 

I had a couple of pickups with the 300. Yes, they are great engine. They did well at 55 mph. It is your project, do what you want. You can sure do it. It is reliable. Long hills with weight and small motors is a recipe for adventure. I was running a 57 chevrolet water truck. 750 gallons of water in the tank. That ol' 235 didn't have near enough snort to make it to the top of the hill. I new I was hosed when I was already in 1st gear with the rear end in low range at the bottom of the hill. Knowing I didn't have any more gear I hoped I could make it. I didn't make it. I don't care about fast, I do want to make it in good shape.

If I was going with a 1 ton rollback or anything along those lines I would go with a diesel. A 6.9 or 7.3 with a turbo would work fine. The Powerstrokes with some giddy up makes me think the good ol' days were not that good. I am not always about pulling at 70 plus MPH. It is nice out here in the western states to run on down the road. My 8000 plus pound pickup with its 6.0 will do 20 MPG running about 70 MPH. The best I was able to get out of my 79 F-150 with its 300 was 15 MPG driving 55 MPH. Like Sammy Hagar, I can't drive 55.

The 300 saw service in trucks larger than F350s. School busses etc.

 

I am so amazed at the replies in this thread.....the honesty is refreshing!!

It always seems someone will pipe in on how their 300 I6 would smoke a Mustang GT while pulling a 15,000 pound trailer up Mt. Everest.


They were always dogs and the longevity was attributable to that they made 150HP in their prime....very understressed.


On a whim I leased a mid 90's reg. cab 150 with the Mazda 5 speed 300 combo....something like $199 a month for 24 months.

Pulling a pair of jets skis up a grade was an adventure and I don't recall any great MPG to justify the slug like performance.

 

Can you do it? Yes. Will it last forever? Absolutey. Will it get the worlds best mileage? Probably not. Will it get better mileage than a v8? Most likely. Will it be fast? Hell no.
Build it and find out. Pretty much some of the only way to answer your question.

 

That amount of weight a rollback weighs, I doubt you’d see any mileage savings.

I would absolutely do a 300 in a F150. Beyond that, no.

 

The more I think about this you might as well just find a fuel injected 300 and hook it up to a NP 435, or Borg Warner T 18 or T 19 4 speed transmission because you will need the very low first gear and the overdrive gears found in 5 speed transmissions probably won't ever get used on this rig you are wanting to put together. You will probably be much better off to just find a working rollback truck and purchase it and go with whatever engine is in it likely a 7.3 IDI diesel.

 

Lot's of good advice here. I am a 300 adherent, I'm not quite sure why. I have had a couple and I always toyed with the idea of "building" one for greater performance. I never did because I was concerned that the results might not justify the cost. My verdict, considering the performance and fuel mileage, not worth the trouble. Esp in an F350. But an 1-300 six will do anything you ask it to do but it will do it very slowly and with no savings on gas. I don't have one now but I still think about the building idea.

 

An idea I have toyed around with taking an Allis Chalmers 2900 turbocharged diesel (301 cubic inch found in a 190XT tractor) and putting it in an F 350 4wd. Probably still wouldn't win speed contests at 100 hp but it would be rather unique chore truck, and that engine has the best sound!