Either the old carb was pouring gas into the engine thru leak, blown power valve and cracked castings or you are stretching the truth. The 750 has larger venturis and throttle bore, which equate to worse atomization and worse combustion, hence worse gas mileage. And that does not take into account the second accell pump and the secondaries opening to soon. So I gotta call BS on this one.

 

1979 F-350 cab/chassis tipping the scales at 6950lbs empty. '71 429, 600 cfm vacuum secondary Holley carb, ported exhaust ports, stock manifolds, dual 2 inch exhaust, turbo mufflers, 4 spd.....16.5 mpg. With a 5spd I'm sure I would see 18. The 429/460's are literally being choked by their ports. They don't need to be made bigger on a truck motor, but they need to be "adjusted".

 

Hi Trent,
You didn't give much info on your 460 aplication.
I would half to say all the things that are out there especialey the tornado's are onley going to help the guy selling them. I would be warey of aney thing that you put in your tank or magnets that are somehow going to give better milage.The onley aftermarket things that will help are things like a MSD spark box, a good aftermarket free flowing air filter, good free flowing exaust. You can go on indefinatley,but it onley gets more expensive and yes slow down lol.
I am installing a low speed stall torque converter with less slipage than stock hoping it will help.
Where are you in Texas? I am in FW.
Bill

 

I put a rebuilt 460 and a 5 speed in my 75 Supercab and am getting 18 highway so yes it is possible. I took the C6 out. I couldnt believe it at first. I kept testing and testing thinking I must be making a mistake so finally I put a portable GPS in the truck to make sure the speedo was accurate. I have my timing at 14 which is a little much. If I take it back to eleven maybe It'll drop to 17 -Not sure. Even at that most of my driving is not highway so I see about 12 which is still better than the 8 I used to get with the C6.

 

What tranny you got? The Ford ZF or the Dodge/Chev NV 4500?

 

I got the NV 4500 and put it in with an Advance Adapters kit. There are a couple of pictures of it in my gallery. The whole setup is rebuilt 460, new edelbrock 750, new stock duraspark, 3.73 Dana and stock size tires. The engine turns 1800 at 60 mph. I dont carry any excess weight-not even a spare tire. I used a 78 Bronco as a donor vehicle for bellhousing and equalizer supports. All other things I bought new at Broncograveyard. Clutch disc is a Chevy 12 inch. I submitted an article on it but it hasnt appeared yet.

 

I'm running 39" Mickeys with a 9" lift on my '96 F250 w/ EFI 460, stock air cleaner and exhaust/ 5 speed ZF gearbox. I get 12 MPG hwy/ 8 city. The huge diameter of the 39" tires really slows the engine RPMs down for highway driving in 5th gear.

 

Way cool. I have the same truck of 1977 vintage, with 400/4spd waiting for the conversion to 460/4500. The truck only has 45,000 miles on it, and I only use it a little in the summer, so I'm working on other projects right now seeing as it works so well as is. The motor gaskets are shot, so I won't be pushing the project too much farther into the future. Looking at the winter of '06-'07 to do it.

 

If your sure your gonna do the conversion watch for transmission jacks to go on sale at Harbor freight. Thats where I got mine for 100 bucks. The NV 4500 weighs 200 pounds so is pretty tough to try and manhandle. It's a nice winter project. Count on it taking longer than you think, but since you already have a 4 speed your already have alot of problems solved.

 

I still think using "460" and "good gas mileage" in the same sentence is an oxymoron!

 

I'll be pulling the cab off for a new frame and full body paint job. Tranny will be going in from the top, and the cab will be set on the frame with camper jacks. It will be my 4th frame off. I'm trying to get decent at them becouse I have a 1965 442 convertable I will be doing a full resto on in a few years. I hope to get good enough so the car comes out right.

 

It all depends on your definition of "good". To consistanly be in the upper teens for mileage with a powerfull big block in a work vehicle, to me, is "good". It's better mileage that I could get out of a 400 in the same exact truck. But, when you look at the whole picture, it's not as good as other options. I got 19.6 with my 4x4 PSD 5spd. It was too bad it was in the dealers garage more than mine.

 

Agreed. Probably more accurate to talk in terms of acceptable versus impossible. But no matter what the mileage, guys like us are way ahead of the game if we have no payments, do our own repairs, and have cheaper insurance.

 

In keeping with the "do our own repairs/do it your self" theme, you dont need to spend $600-$1000 to get a good "street" port job on a 460 that could help your power/milage.

Get a few carbide bits and spend $25 to join Scott J's Reincarnation Automotive site, http://reincarnation-automotive.com/ for good info/pics/air flow numbers needed to port the different types of 460 heads yourself (street or race combos).

 

yup there are only so many things that can help with me i did new rear gears headers + 3in exhaust recurve distributor better intake and most importantly accellerate slower and drive slower cause 460 and gasmilage don't go together in the same sentance and btw i get 17 MPG in my 77