okay so I got a 460 given to me yesterday and I was going to put it in my 78 f-150. but I wanted to know some things first before i do it.

first what kind of fuel mileage will the 460 get compared to the stock 351m that my truck has now?

second. is it possible to make a 460 get 15mpg or higher?

and third would swapping in the 460 in my truck be worth doing vs rebuilding another 351m engine?

 

the 351m was by no means a fuel miser engine and neither is the 460. i would suspect that you will get 1 - 2 mpg less with the 460 compared to the 351, but you would gain a whole lot more hp and torque.

you could probably build the 460 with some porting work on the heads, a decent exhaust system and headers, a cam picked for low end torque and mileage, a 600 - 650 cfm carb, rear gears in the 2.7 to 3.25 range and keeping your foot out of the pedal, you might be able to *** 18 - 20 mpg out of it, maybe. more then likely 13- 16 mpg. 460 were never known as fuel efficient engines even with EFI.

tough call, 1/2 dozen of one 6 of other. to put a 460 in you will need to find the motor mounts and towers and all the little stuff, might have to reroute some lines and wiring, but you can keep your current tranny as it will bolt right up to the 460.

other option is to rebuild your 351m into a 400. same engine just different cranks (i am pretty sure the rods and pistons are the same). the 400 is an under appreciated engine. from the factory there are severely handicapped with smog equipment, low compression, small cam and 2bl carb. just by upping the cr to 9:1, a decent cam, 4bl intake and headers, these engines make some suprising hp numbers. the 351m is limited by piston selection as the factory setup puts the piston way down the hole.

food for thought
Mike