Hello,

86 F250 460 4sp don't know the final drive ratio but it is a 2wd and turns around 2500 rpm at 60 mph.

Just rebuilt the carb, fairly satisfied with the rebuild except I seem to have a slight surging aroung 1500 rpm.

New: Cap, rotor, wires, platinum plugs.

Tires at 80 psi.

Towed 5th wheel 30ish miles and it took 1/2 of my back tank.

This equals 9.5 gallons for 30 miles = 3.15 mpg!
5th wheel weighs about 5500# and is empty. I took it real easy all the way.

I did drag it up two Large hills. Once to my house and once to my parents. Mostly freeway miles however.

I am going to check the timing tonight. It may be retarded.

Any thoughts? I am going to have a hard time camping at $.65 per mile for gas alone.

Thanks,

Larry

 

First of all make sure what you are getting in the way of mileage just looking at the gauge isn't very accurate. Second eight mile per gallon is about the best you will get if it ever gets ten count your blessings. 3.55 rear gears is about as tall as you will have more that likely it has 4.10 gears in it.

 

I am aware of all of the above. I was being conservative with the guage. I would be ecstatic for 10. A 300% increase.

Larry

 

I have an 86 F250 460/C6 combo which is very close to your truck.

You mentioned that your truck took 9.5 gallons or half of your back
tank... my truck has dual tanks as well... it was my understanding
that the back tank is closer to 11 gallons not 19 with the front being
around 15 gallons.

If your truck took half the back tank, it would be 6.5 gallons which
would bring your mileage up to par.

Course if I wrong, nevermind then!

Scott

 

I believe the tanks are 19 gallons each. I hope I am wrong!

Larry

 

I have a loaded 1978 F 150 Ranger, XLT, Lariat, Towing Special, 273 Locker. It has duel tanks and the rear is much smaller. It is the auxilary tank and holds around 10 gallons and it is located high up under the bed at the rear of the truck close to the bumper. Above the spare tire. Where the front tank is the main and takes close to twice the fuel. I think around 19 gallons to fill and it is located along the inside of the frame. Take a look under neath and you should see there is a big difference. On the basis of that you may have just doubled your mileage. My 460 with the AC on when it isn't under load gives me 14 MPG mainly highway and I am very easy on it. I set the cruise at 55. Under load towing I am luck to get half that.
Ric

 

On the 80-up long bed trucks, both tanks are 19 gallons a piece.

 

Ditto, 19 + 19.

 

I could always hope I was wrong.

Thanks everybody.

Larry

 

I'm just going by how many gallons I can get in the tank when
the gauge reads empty - 10 gallons rear, 15 gallons front.

I've read where you can get an "extra capacity" fuel tank, but
from what I've seen, the tank is the same size, but the filler neck
doesn't go as far into the tank, giving it the extra capacity.

Scott

 

Clifford, It sounds to me like you have the same problem with your fuel gauge as I. When I fill the tank, the gauge reads full, but when it reads empty, it only takes 9 - 10 gallons to fill it. I ran the tank completely empty (the beauty of having two tanks) and when I filled up, it took 19+ gallons. I can run both tanks on empty (or so the gauge tells me) for quite a while.

 

btw, most auto F-250s I have seen come with 3.54s... I've seen many manuals with 4.11s

 

my '86 has the 4.10 rear with a c-5. I get 11 empty, 9 towing a 3.5K trailer

 

thats probably a C6.

 

I was getting lousy mileage with my '82 F150- found out the front brake calipers were dragging a bit at all times- killing my mileage.

New calipers helped mileage- they don't stick.