460 Daily Driver questions

1986 F-250, 4x4 SCLB, 460, C6, 4:10 gears.  Holley 600cfm carb.

I’m in the middle of building a new 460 (OEM spec, straight-up timing).  C6 just got a fresh rebuild, and a new torque converter.

I know this old girl only gets about 10mpg (I’m assuming the new engine will be no different)..

My question is this, do y’all consistently get 10mpg?  Or does it drop significantly with city driving, or running 80mph on the highway.

Is the 10mpg achieved by only running 55 on flat highways?

I’ve had this truck for about a decade, but I had it as a plow truck at my cabin and only drove her on the roads a handful of times - and the last few months I was driving her daily she was running on 6 cylinders (7 & 8 were full of coolant and leaking heads), so I never really got a chance to test out her mileage in various scenarios.

I love driving this truck, so I’m tempted to make it a DD (and slide-in camper for adventures).. but I’m curious how ya’ll’s mileage has been when DD the 460.

Not a 460, but my F150 does have a C6 transmission that is absolutely worn out with a calculated 13% slip.

With that said I used to get 14 mpg city till the switch to ethanol blended fuel, that 10% ethanol at all pumps in my area saw me drop down to 12 mpg city in the summer time and 10 mpg city in the winter time (result of my drive to work being so short the choke never got hot enough to fully open).

Highway at 70 - 75 mph I was seeing 15 - 16 mpg with the ethanol blended fuel.  Thats why I decided to go aftermarket EFI on the 302 I am building to replace my smog engine to try and hit 15 - 18 mpg city and 18 - 20 mpg highway.

I used to own an 86 much like yours, however I had 3.55 gearing.

I got a little over 11 MPG once, but it was flat land driving and 60 MPH and slower with no load.

Running faster, like 70-80 especially with the 4.10's and she'll drink the gas.

460's are awesome engines, but have a drinking problem.

Big Blue came to me with a well-worn 460 and a T19 with 3.55 gears.  In that guise it would get 11 to 12 on the highway running 65 and I didn't/don't check around town.  Now with a new 460, EFI, and a ZF5 with OD it gets 12 - 13 on the highway at 65.

But it weighs 6600 lbs due to all of the stuff on it, like dual batteries, a winch, an inverter, air compressor, etc.  And I'm running 33" tires.  So there's a lot of mass to deal with.

So with a C6, which has no lock-up torque converter nor OD, 10 isn't a bad number.  And if you include in town and above 65 MPH driving then it is a good number.

When I bought Darth in April 1994, once I fixed the Holley 4180 and installed a straight up timing set I would get a solid 10 highway at 55-60, when we finally got better speed limits, still 10 at 65-70. Towing the 5th wheel. 8 at 55-60, worst, running 65-70 following a group into a 35 mph headwind, 6 mpg.

After converting to EFI and installing the E4OD, but probably only having a compression ratio on the order of less than 8:1, I got 12.5 mpg running almost all highway at 70-75 mph. The aluminum camper shell helps reduce wind drag.

I’m planning to put an 1800lbs slide in camper in the bed..

I’m guessing probably 8 mpg with that..

Don't know how much our 9 1/2' self-contained camper weighed, but in our '72 F250 w/a 390 4bbl and a C6 we saw a high of 9 and usually ran in the 6 - 8 MPG range, with wind playing a huge part of the equation.  Doubt the 460 will do much different.

Gary Lewis wrote

Don't know how much our 9 1/2' self-contained camper weighed, but in our '72 F250 w/a 390 4bbl and a C6 we saw a high of 9 and usually ran in the 6 - 8 MPG range, with wind playing a huge part of the equation.  Doubt the 460 will do much different.

Doubt so also, all the big blocks drink down the fuel.  About the only way to get any kind of mileage while having the torque of a big block is to take and go with diesel but still are limited by the design of a truck not being designed to be aerodynamic.  Not even the late model trucks are much better than the old trucks in the aerodynamic department.  Their mileage is from the use of OD and lock up converters in conjunction with EFI.

The 5.0 Coyote we installed in a lwb '82 F150 with a early 2000s automatic mustang transmission was able to get that truck put down a decent 20 mpg highway with a bed cover on it.  Thats about on par with Ford trucks of the same era as the 5.0 Coyote with the same engine.

On the C6 what would help them out is supposedly today if you rebuild them like Broader Performance does you get less slip than the Ford built units as they were when new and you also have better converters like the XTM from Hughes which I will be running in my Broader Performance Wide Ratio C6, that converter is supposed to have less slip than OE converter, better torque multiplication than OE converter, and it pumps I think it said 2 gph more than a OE converter for better cooling.  Still it wont be on the same level like say a E4OD with its lock up converter but it will be a day and night difference over a Ford OE spec C6 though.

Thanks guys!

Yeah I rebuilt the C6, and got a new Hughes TC that’ll go in when I put it all back together.