460 MPG I can expect?

[Kurt Combs]

I have a F250 with a 460 out of a 77 F150. I changed the timing gear set to zero degrees, installed a performer intake with a holley 600 CFM and recurved distributor. The rear gears are 3:54, the tires are 31" tall and the tranny is a C-6. I get just a hair over 10 miles to the gallon. (When I was running a stock 360 I normally managed about 13 miles to the gallon.) I am wondering if this is all I should expect with a 460 or should I consider an Edelbrock carb to possibly improve the mileage?

[Norton]

I just bought a '71 Highboy with a 460 out of a '76, don't know what model. It has an Edelbrock 600 CFM with stock intake. Obviously it's 4WD, and it's got a 4-speed with 410 gears. On the 1100 mile drive to get it home I got about 10 MPG at 70-75 MPH.

[BobbyFord]

That's better mileage than I get but I'll get to my destination before you...that is if I can make it past the next fill-up station

[derbydad276]

its a 460 who cares?

if you want fuel milege put a diesel in

[Kurt Combs]

When the 460 wears out I might consider a diesel. However I really like the quick response a 460 supplies. I don't think I would get that with a diesel. But on the other hand, 20+ mpg out of a 3/4 ton bump would be cool. Hum....... but the real question is am I losing mpg because of a poorly performing Holley, or am I getting the best mpg I should expect? I guess I forgot the Holly carburetor part of the question. I also sometimes notice the inside of the tailpipe is black, which I interpret as running rich. The black tailpipe is after running down the freeway at 65-70 mph. So, if 10 mpg is normal I am happy, but I sure wish I had posi-traction for when I punch it a little too hard and that peg-leg spins one tire.  

[caseyj10]

I looked on Ford trucks website and a dent with a 460 usually gets 9-11 city and 15-17 highway. you shouldnt feel too bad about your mpgs though, i drive a 2001 ram 1500 with a 360 everyday and only get 11mpg...... no matter where or how i drive.  

[Ranchero50]

Pick up a cheap air/fuel meter and a basic 3 wire o2 sensor and you won't have to guess.  It helped me a lot when I was tuning my twin turbo'd capri with the 351 and holley being blownthrough.

[cdeal28078]

I think 10 is pretty fair for a 460 but I think it can get better. I don't think it is the Holley unless it is just set up wrong.
clint

[Kurt Combs]

Well, the Holley wasn't setup, it was just installed. I have no idea what it came off of, but I threw a kit in it and it runs.

Here is the history of the Holley: I bought the engine from the college where I work after it had been "rebuilt" by the shop teacher who then retired. I think freshened up is a better description of what he did to the engine, new bearings, rings and ground the valves. He removed the Ford spread bore and used a Q-Jet adapter to make the Holley fit. The new instructor sold the 77 dent to me because it would not pass California smog tests with the Holley carburetor. So, I of course put the engine and tranny in my bump and added a Edelbrock Performer manifold to make the Holley bolt on correctly. I know nothing about setting up a Holley, so it was just bolt it down and go. I subsequently put a kit in the carb and it seems to run okay other than cranking a few times when hot before it starts. At this point I would have to say it is the first vehicle I have ever owned that I could actually see the gas gauge dropping while cruising down a freeway. If I could get back to around 12-13 mpg I would feel a lot better about the conversion from a 360 to a 460.

I do feel really, really, good about the increase in power. Did I mention that it can accelerate like mad going up hill in the passing lane? This has to be a surprise to a few folks when a white haired baby boomer in an old truck rockets by them.    

Anyway, back to the carb question, I am opening to suggestions on get better mileage that relate to the carb.

[1970 Hi-Boy]

I would not concern myself with the black insides of your tail pipe. I've always looked at spark plug coloration for rich/lean of an engine. They should be a light brown/tannish looking color. If your plugs are running real dark/blackish looking then switch to a smaller size of jets. There are books available on tuning the Holley carburetor, and would be a good investment to really get to tweaking your carb to your engine. As for mileage I personally would not be looking for any large gains here. Do the normal things like airing up tires, engine in good tune, and clean air filters and the like other wise you can try running a good quality synthetic oil in your engine, transmission and rear end, this will give you a gain in fuel mileage, look for the biggest gain in the rear axle as this is where the power from the engine is split to meet the road, and a high friction point. Any friction reduction you can make will save you at the pump. The 460 I used to have got between 7 and 8 mpg, but I could never keep my foot out of that thing. Have fun with your tuning, as you may have to do it numerous times to get everything jut right.

[cdeal28078]

I suggest getting the how to tune a Holly book also plus use the internet to look at the numerous articles on how to tune it. There is a lot of info for free out there. Tune the jets, the accelerator pump cam and shooter and the A/F metering screws for best performance. There is also a lot of economy and performance gained by tuning the lower valve.
clint

[67 428 F250]

I have a F250 with a 460 out of a 77 F150. I changed the timing gear set to zero degrees, installed a performer intake with a holley 600 CFM and recurved distributor. The rear gears are 3:54, the tires are 31" tall and the tranny is a C-6. I get just a hair over 10 miles to the gallon. (When I was running a stock 360 I normally managed about 13 miles to the gallon.) I am wondering if this is all I should expect with a 460 or should I consider an Edelbrock carb to possibly improve the mileage?

Hey Kurt, I have a 67 F250 4x2, 428 (synthetic, clutch fan, tuned for regular fuel and currently no headers), Edlebrock 600, 2 1/2" dual exhaust, NP435 (synthetic), 3:54's (synthetic),Eaton Elocker and 31" toyo's. Driving a "round trip", up and down elevation, holding the speed at 55 MPH I got 15.3 MPG. Going back to headers might help a bit more but the only thing that is going to make a real difference will be taller gears. I don't think your going to get any better with that C-6.
I was considering putting a C-6 in mine but I will get less MPG, not sure what % less, because the torque converters do not lock up.
Will

[Kurt Combs]

Will, thanks for the post.

I will have to try holding 55 mph and see if that makes a difference. You are also running an Edlebrock which might make a difference compared to my Holley 600.

[67 428 F250]

What year is your F250?

[Kurt Combs]

My F250 is a 1972 and looks to be the exact same color as yours. Nice looking truck!