Who has some real world numbers from a 4x4 with 33"/35" tires and a 440 with 400+ HP. What could a fellow expect the mileage to be on a motor of this caliber?

probably around 6-8mpg would be my guess.

Back in the early 80's, I had a '75 Ramcharger with a stock 440, 3.55 gears and 33" tires. That thing got 8 MPG whether it was towing or not towing.... Certainly was no rocket but it had nice torque. With a little more horsepower as you have mentioned and some compression, I still doubt you'd ever get over 10 MPG.

My old 86 W250 with a 440, 4 spd, 285/75/16s and 4.10s got terrible mileage. Less than 8 mpg in most cases. However, I never expected it to get very good with a 850 double pumper on it. I didn't care what it got, just as long as it ran good. If you want mileage, you need to go diesel.

i have a 78 3/4 ton with a 440 that gets around 6,it has a loose converter,4.10's and 35"tires,i use an 800 holley,10.0 to 1,nice cam ported heads,prolly makes 450-475 horse maybe.

Almost all 4wds with 3spd autos no matter what motor got 10 or less that I've seen.
I had a 400/727 3.23 295/50s and got 11.4 when driving easy and 4.6 when getting on it and it was a very mild motor. Don't plan for more than 10mph. Plus its a truck with a flat nose

10 on a good day-78 400 runs 11 with a tailwind,8 usually

My 93 Ramcharger with the rebuilt mild 440 was getting 8-10 mpg on average.

This was with a 727, 34" tires, 4.10 gears. 95% highway use. Never drove it over 60mph.

It now waiting for the remainder of a 518 OD swap.

Sounds like 7 to 8 is a pretty average number. Thanks everyone.

all though not a 4x4,my 88-440/727/3.91sg with 29x15x15 M/Ts got a flat 10 mpg.

swaped in 3.23 with a new q-jet/performer RPM intake and picked it up to 13 mpg.

hoping a 2.76 gear will net me a couple more for 15-16 mpg. then I could drive to the next town over for more gas.

I gave up on mpg in a 4x4 muself.

My "truck" (motorhome) .... was getting 12 or so ....with a TQ and Streetmaster intake(way better UPgrade from the OEM garbage) .... but later on - with a new-tech cam, head work, exh work, going from a 4.56 to a 3.73 gear and more compression(flat top pistons) it will get 16 ....and I have been challenged on that .... two people have bet me it can not be done .... so I have two bets - a total of 3500$ !

NO real trick there cf ... just keeping the MPH around 60(the MH is a pretty AERO piece) ..... and putting on a better fuel delivery combo .... that being a TQ and a StreetMaster intake. THEN playing with the metering rods

Now my 16 mpg mark is NOT going to be an average of say a trip from MI to FL ... it will be with a measured 1 gallon container ...and will be run on-the-flat.

HONESTLY .... I think that it will be closer to 18

...with the new cam, compression, SP2P intake and the gear change.

I dont see a big camper getting 16-18 if the trucks with a 318-360 barely pull that with 3.23grs. Good luck

My 78,000 mile 74' Ramcharger with the unmolested 440, fulltime 4 wheeldrive gets 9mpg. The only time I've checked it is during the cold weather. I've had a tough time not modifying the motor, I know I can make it better.Dave

Is this worthy of additional chat ?

My 1980 W150 shortbox had a 440 auto w/3.73 gears and 35" tires got 8 mpg & 1985 W350 440-4speed w/4.10s and 235/85R16's gets about 8

What are the driving conditions?

8 mpg ? ... only a from the least coast of Florida could continue dealing with those conditions!

I am up for it. But, you already know what I am up to. Was it 440 or 413 you were running to get 12mpg? That is pretty impressive for an RV.

My 413 heads are going to the machine shop tomorrow to get cleaned, magged, and shaved. Then it will be time to get after the chambers with some roloc grinding discs.

I am thinking about just doing a basic clean up of casting flash and overhangs between the port and exhaust valves. There is a BIG overhang in the runner just behind the bottom of the pressed in exhaust seat. I wonder if there would be any mileage gain from a 3 or 5 angle valve job on the intake side? Exhaust I think I want to keep the nice fat seat contact width for cooling.

It will be a while before I have any numbers with the new engine, but will get baseline gas mileage numbers with the old one this summer.

Anyone have any experience with a do it yourself ceramic coating for piston tops?