Hello all and let me say I am super happy that google took me here!

I have a 1984 F-250 HD 3/4 Ton with a 460 CI 4 BBL Carb.
We used this truck to tow our race cars all over the west and it done it's job very well.

No longer towing our race cars with this pickup since we upgraded to a 2007 Super Duty Diesel ..

But I want to use the 84 for camping with an Cabover Camper and here is where the problem is.
The 460 get's an amazing 8.5 MPG city or hwy no matter if it has a load or not.
Needles to say I really don't want to spend billions in petrol to go around the west with a camper.

So I'm looking to swap engines on this beast to either Gas or Diesel.
I would like to get at least 15 mpg out of this Truck. After talking with some friends with Injected Gas powered pickups I see that they are getting truly good MPG ratings.

I'm considering going to a 351 or even a 302 Carb engine or a Diesel if I have to.
My question for all of you is how hard will it be to put a small block into this Truck and is it worth it ? Or should I just go to diesel ?

With the small block engines I can upgrade the million LB Transmission to a AOD Unit and that alone would help with MPG. Heck just loosing the intake manifold off the 460 would help. Ever lift one of them things ?

Any suggestions would be helpful.
Thanks
Joe

 

Good luck.

It's a heavy truck designed for heavy duty uses, not exemplary gas mileage.

What is your rear end ratio?

You should fill out the rest of your profile so we can see where you're at.

Yes! I ended up using the cherry picker to remove mine (with engine
installed in truck).

 

3.70 or so on the Diff .

I updated me profile

I know it's a HD Truck. Just seems to me that there should be a way to get the fuel mileage up . The 460 is a pig at best LOL.

I don't need tons of power anymore as the camper will weigh less than 3000 LB when loaded. And I only need to go 65 MPH LOL . So I'm looking to bring the truck to better fuel mileage by changing engines or upgrading to a Cummings Diesel.

8 MPG is just plain stupid IMO with todays Gas Prices.
And I am not in the mood to spend 60K on a new truck. I would rather spend 5-7 K upgrading this truck as it is in very good condition.

The Super Duty we have is for towing the race cars and there over grown trailers.
So I have to use the old F-250 for my Camping stuff.

Anyway thanks for the reply and I'm looking forward to any info on this kind of thing.

 

If you want 15mpg with a cabover camper, you are definatley talking diesel, and even then, just due to the nature of a cabover camper and the drag they create, it won't be easy to get.
Since you mentioned a Cummins swap, that is a very good option, but, it ain't all that cheap to do....

 

Thanks for getting back to me so fast

Yea it's looking like I will be looking for a wrecked dodge as a donor truck.
I think if I go that route I will use the Mopar Auto trans and loose the 300 LB cast iron four speed

It looks like the Cummins will do the job well. Also I can save some cash by doing the mounts and such in my shop. Will have to do new drive shafts and lots of fun with clearance I'm sure ..

I guess what I am looking at is to see if the Small blocks will up the MPG.
Looking just a the weight I would be ahead with the small blocks. Also if I go that direction I will use a over drive Auto Trans. Not sure of the AOD has the guts to handle the weight of the Truck and the Camper . Will have to research that also.

It sure is a lot easy're to build a race car than upgrade a old Pickup LOL.

 

In that kind of useage, a smallblock is going to do the same as the 460 or worse. Running around unloaded is about the only place you will gain anything, and even then, hitting your 15mpg target unladen may be an issue.
I ran a couple different engines in my 81 before I dropped it's cab on the diesel chassis, reg cab stepside, truck weighed maybe 3700, no load ever, 3.50 gears, the 302 did 15 with an OD trans, my 300 did about 16 with a 4 speed, and the 351W did 12, which is about the same as my 460 still does.
My Cummins OTOH, the thing weighs 7000 lbs, is as aerodynamic as a brick, and if I drive it for mileage, I can squeak 22-23 out of it, normal driving returns 17-18

8.5 unladen is odd, I can still squeak 11 out of mine on 38.5 Boggers with 4.10's and a not very stock engine...

 

As cool as a Cummins swap sounds, its not really that much a financial advantage. Look at the numbers:

A Cummins swap is probably going to run you around $6000, that's what another member on the board quoted it cost him. At $2.70 a gallon and 8.5 mpg that would buy you ~19,000 miles of driving.

Furthermore if you do the swap and the cummins gets you 15 mpg at $3.00 a gallon for Diesel it will cost you ~ $.20 a mile in fuel, compared to the ~$.32 for the 460. So $.12 a mile difference. Therefore to make up the cost of the swap alone it would take 50,000 miles of driving. And this isn't even counting the extra costs of maintaining a diesel.

Like I said, a Cummins swap is pretty cool, but I don't think saving money on fuel is a good reason to do it to a 24 year old camper truck.

 

I would try changing the rear gear and leave the 460 in it. I just got through a 2000 mile trip with my 89 with a 7.3 diesel, c6 auto and 4.10 rear gears, and got 10.5mpg the whole trip.
They are right. It's going to take a certain amount of fuel to move the camper/truck combo through the air, no matter what engine/tranny you have. When I got to flatter terrain, I could have used overdrive to help my mileage, so that's what I am doing now, putting in a zf 5 speed.

 

Perhaps I should look at this approach ?

1 Move the 460 4bbl off and go to injection from another year of pickup ?
2 ZF Five speed and 3.50-3.55 rear gear ?

Just by loosing the Stock intake and the cast iron transmission I would gain a tad.
Then if I can get it to twelve or so I could live with it.
Sounds vastly cheaper than going to diesel and from what you guys are saying my 460 should be doing better than it is. Damn California Smog ain't helping I bet.

Also I want to thank you all for your ideas and I love that thinking that is being used here. Thanks all.
Joe

 

I would do the zf and the gear change first. I bet that gets you in the 12mpg range by itself, though you will have to see how it does with the camper on it.

 

I don't know how big of a camper your putting on this thing, but even your 12 mpg goal could be high expectations. I guess if its a 2wd with a ZF and 3.55's and you keep the speed down ya might get there.

For reference we have a 1990 F250 4x4 with a 460 and ZF-5 and 3:55's and it has never got better than 11mpg empty.

Even my 2000 Superduty 4x4 with a 7.3 and a ZF-6 would only get 12mpg pulling a 16x7 enclosed trailer, and 10mpg pulling a 24x8.5 enclosed.

 

Ah Camper Specs

11 FT and about 2500 LBS.

I'm still looking at all the options. The Truck is a 1984 F -250 HD with Extra Cab.
Two Wheel Drive . 4 Sp and 373 Gears in the back.
It has Air , Power Steering .

I have Friends who are getting in the 16-18 range with 350 Injected Chevy Pickups.
I also have friends who were getting 14-15 with the old 6.9 Diesel setups.

Might just have to bight the bullet and get another truck.
Heck even my 2007 SD TWD one ton gets 13 MPG empty and 11 with a 32 foot car trailer with the 2250 LB Late model Stock car and all of it's stuff. Even an extra engine for those really bad nights.

The One Ton out weighs the 250 buy a fair bit.
It just bugs the heck out of me to see a solid truck like this 250 go to waist over a MPG issues.

The reason I want to do the work on it for the camper is it would really be nice not to spend 40-60 K on yet another truck LOL.
I would just use the 2007 ,. But it has to work and it would make very little sense to unload it every month or so to put the camper on it.

Was just looking at upgrading or changing to EFI. Wow what a can of worms that is LOL.

 

Are those Chevies of the same vintage (25-30 yo)?

Yep....

 

Go diesel or leave the 460 in it, if you try to do cab-over camper duty with a 302 or even a 351w, you will work it harder and get the same mpg as the 460 or worse.........Leave it as is.

Example: My 93 F-250/460 - 11-10.5mpg w- 9.5ft Lance camper @ 2450lbs + 2200lbs of boat in tow + gear.

My buddy's 94 Chev 2500/350- 8-8.5 mpg tops pulling a almost identical load to mine, I might add, screwing the snot out of his 350 climbing passes that the 460 loafs over.

Big motor loafing and getting 10-11 mpg is better than a small one screaming it brains out at 8mpg to do the same work..........Its gonna last a LOT longer too, that 350 is already making "suspect" noises at 85,000 miles.

 

Yep I agree after doing a days worth of research .
I'm going to do the ZF Transmission update and drop the rear to 3.55 or less.
That should get it to 12 or so if I don't run it hard.

Thanks for the info gang!