Hi! i have a ford f100 1956 with a 390 engine and it beeft up with edelbrock 750 carb, and edelbrock intake .compcam nr 33-226-4 .headers 9" rearend with 3.50 gears.its a nice streetdriven car but the car drink so much gas it kills my economy any tip? to big carb maybe?

 

I think you would see some improvement with a 600 CFM carb. Also the 3:50 gears are a little low for highway cruising, something around 3:00 would get you a little better mileage. A lot of folks build these old trucks as "hot rods" and never give much thought to economy.

 

FE engines weren't built for economy, it just wasn't part of the program back then. I'd be surprised if there is much you can do to get more than 10 - 12 mpg. What are you getting now?

 

Both of these guys are right. 750 cfm? is this a 4bbl? Friends I know with 390's never got any better than 12 mpg. Then again, they could never resist to get their foot out of it, lol. If there's highway driving involved, I'd simply consider an OD trans swap.

 

BINGO!

I have almost the identical set up except I have a 9 3/8 rear geared at 2.80:1 which is perfect for the freeway - 65 mph @ 2400rpm.

I'm getting about 12 maybe 13 mpg on the perfect day. But it is very strong. Theres no effort going up hills - even big ones, and when I hit the gas, it moves - very quickly.

Want power.....FE.

Want mileage......289/302

PS Havi and I were typing at the same time. That 750 CFM is a BIG four barrel - almost a complete duplicate from the Carter Four barrels. When I took mine to have the Carb adjusted for th efirst time, the folks at San Diego caburetor told me the 750 was "almost too much carburetor for that engine - not quite, but almost."

 

Yep, It's the nature of the beast........I agree though, taller gears would help a little. Less RPM = less fuel burned. BTW, how much does gas cost over there? You're in Sweden, right? T/M

 

Well i must have wrong about my gears in the rearend i drive allso 65 mph 2400 rpm.But something must be wrong the car takes nearly 1 gallon at 6 miles and the fuel here in sweden are expensive.

 

There are many other factors that affect gas mileage as well; terrain, stop & go driving, tire type (rolling resistance), vehicle size and weight, and vehicle aerodynamics. As was stated, the gas mileage is usually not the intent of hot rodding an old truck; you are basically driving a heavy brick.

Today’s vehicles have the advantage of a computer dynamically changing the air/fuel mixture to try and achieve stoichiometry ( complete combustion). Carbureted engines can be tuned but there is not much you can do outside of changing the jets, adjusting the fuel/air mixture, and proper setting of the floats. By adding a cam, you have changed the valve timing which primarily allows the valves to be open longer for more power but at a reduction of gas mileage as well.<o></o>

None of the solutions offered are cheap, i.e., a 600 cfm carb or higher gears for the rear end. You are working with an equation of diminishing returns anyway. I have a ’56 F100 with Chevy 350, 600 cfm carb, and get only 10-12 mpg around town. If you were to get an additional 2 to 4 mpg, what cost would you be will to pay for it up before you hit your break even point?<o></o>

 

There are two things to consider: First, does your rear end have an ID tag? It is a small metal tag that will be bolted to the front face toward the drivers side. If it does, let me know what the number is in the lower left corner - that is your gear ratio.

Second, I also thought I was getting very poor mileage. I would runa full tank of gas and divide by the number of miles on my odometer.

Well, come to find out that when you are sittin gup high like we do inour trucks, you do not have as much sensation of speed. With my rear end and wheels I was actually going 65 when my speedometer said 55. That means your odometer is off as well and you may be driving faster (and subsequently FARTHER) than you think you are.

I would have the speedometer/odometer checked by a shop, or have a friend fallow you and "clock" you over a 5 mile (or XX KM) course to see if your instruments are accurate.

I gained 3 MPG with that correction alone. You should be getting about 10 to 12 Miles per gallon - on the "highway" with your set up. In city driving it will be about 9-10 max - depending on how much stop and go you do......But hey......it ain't no Volvo!

OBTW, here is a gearing/RPM?MPH calculator that is very accurate.

http://www.et-studios.com/motorsports/gears/gears.html

Your C6 gearing is: 2.46:1 (first)/ 1.46:1 (second) 1.00:1 (Drive) 2.18:1 (reverse).

See this site and select C6:

http://www.fordpowerproducts.com/For...erican_lit.htm