fuel consumption
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New User
Joined: Jan 2001
Posts: 5
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fuel consumption
I have a 1976 Ford F-250 with a 390 CID engine and 4 speed standard transmission. It is 4wd with manual locking hubs. On a recent trip of 500 miles I got about 13 miles per gallon. On the return trip towing a 5000 pound trailer I got about 10 MPG.
The two barrel Ford carburetor has size 54F jets. Can anyone tell me what effect using smaller jets will have and what are the smallest jets I should use. I am planning a 3500 mile trip towing the trailer and am quite willing to give up power to get better fuel milage. The trip will not involve any mountain driving.
The engine was rebuilt about 4000 miles ago, uses no oil and as far as I can find out from the previous owner, is stock.
I would also appreciate suggestions about ignition timing.
Thanks
The two barrel Ford carburetor has size 54F jets. Can anyone tell me what effect using smaller jets will have and what are the smallest jets I should use. I am planning a 3500 mile trip towing the trailer and am quite willing to give up power to get better fuel milage. The trip will not involve any mountain driving.
The engine was rebuilt about 4000 miles ago, uses no oil and as far as I can find out from the previous owner, is stock.
I would also appreciate suggestions about ignition timing.
Thanks
Post Fiend
Joined: Feb 2000
Posts: 5,130
Likes: 8
From: Brea CA
fuel consumption
10 MPG in a 4WD towing a 5000 pound trailer is not that bad. The carburetor is jetted lean already, going smaller may decrease your mileage if you have to put your foot into it more. I’d bump the initial timing up to 10 degrees BTDC, make sure your vacuum advance is working.
Barry
Barry
Lead Driver
Joined: Nov 2000
Posts: 6,619
Likes: 340
From: Albuquerque
fuel consumption
If you go any leaner you risk burning a piston.
1977 Ford F-100
400m/c6/4:11/Gear Vender O.D.
Crane hydralic roller, forged, ported polished,Deamon,Edlebrock, yada, yada, yada
280,000 miles
Stock on the outside
modified/rebuilt everything
1977 Ford F-100
400m/c6/4:11/Gear Vender O.D.
Crane hydralic roller, forged, ported polished,Deamon,Edlebrock, yada, yada, yada
280,000 miles
Stock on the outside
modified/rebuilt everything
Posting Guru
Joined: Oct 1999
Posts: 1,188
Likes: 0
From: yes
fuel consumption
first of all take the engine for a drive, let the engine get warm and the oil get warm too 10-12 miles should do, then if you have a open stretch of road that you can pul off to the side on, while the engine is cruising put it in neutral and shut it off if you dont have power steering and brakes, then when you get pulled over and stopped look at the spark plugs, they should have a light tan or cream color, if they have this, your jetted properly, if they are dark, or black you can go leaner, if they are bright white or have black flecks on them and are white your too lean already. if you cant do it on the highway or a open road, try to make sure that you keep your foot as out of the gas as possible while you go someplace where you can check the plugs because the accelerator pump shot might throw off the plug color. another thing you could do is have a O2 sensor put into your exhaust then just get a cheap voltmeter and read it to find out if your rich or lean I think it's .5volts is proper mixture. And like BBB said bumping the initial timing up a little will help some, i gained 10% better milage or 1mpg on my 360 just by going from 7 degrees to 14.
Fleet Owner
Joined: Jun 1999
Posts: 24,552
Likes: 74
From: Creedmoor, North Carolina
fuel consumption
Don, You got a 3/4 ton 4X4 with a big horse and you're bitching about that milage. Some guys just will not be happy.
John
jowilker
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66F100s Rule
In the cool still quiet of night you can hear chevies rusting away.
John
jowilker
[link:www.ford-trucks.net/users/jowilker|Club FTE since 01 01] My FTE Page
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66F100s Rule
In the cool still quiet of night you can hear chevies rusting away.
Postmaster
Joined: Feb 2000
Posts: 2,759
Likes: 2
From: Auburn,Al
fuel consumption
amen to that john,
what kinda gears you got in that f-250, 4.10? how tall of a tire?
1985 F-150/351Ho/c6/4wd
1979 F-150extcab4x4/460/c6/6inchlift w/60rear44frnt
on a quiet night your can hear a chevy (lol,you can watch a dodge) rusting away
what kinda gears you got in that f-250, 4.10? how tall of a tire?
1985 F-150/351Ho/c6/4wd
1979 F-150extcab4x4/460/c6/6inchlift w/60rear44frnt
on a quiet night your can hear a chevy (lol,you can watch a dodge) rusting away
Lead Driver
Joined: Nov 2000
Posts: 6,619
Likes: 340
From: Albuquerque
fuel consumption
Heck, I'll have a party if I get my truck up to 11mpg.
One should be sure the speedo is correctly geared before checking gas milage.
1977 Ford F-100
400m/c6/4:11/Gear Vender O.D.
Crane hydralic roller, forged, ported polished,Deamon,Edlebrock, yada, yada, yada
280,000 miles
Stock on the outside
modified/rebuilt everything
One should be sure the speedo is correctly geared before checking gas milage.
1977 Ford F-100
400m/c6/4:11/Gear Vender O.D.
Crane hydralic roller, forged, ported polished,Deamon,Edlebrock, yada, yada, yada
280,000 miles
Stock on the outside
modified/rebuilt everything
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Thread Starter
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New User
Joined: Jan 2001
Posts: 5
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fuel consumption
I have 4.10 rear end gears and 235R75/16 tires with duals on the rear.
Please remember I am using Imperial Gallons, which is about one US quart more than a US gallon. I am not complaining but just wish I couls do better. Gas here is 69.4 cents a litre and it takes 4.54 litres to make an imperial gallon. I used to use a 3/4 ton 1968 Intrernational with a 304 engine and 4 speed std. trans and get about 15 MPG towing a 25 foot travel trailer.
Thanks for the responses.
Please remember I am using Imperial Gallons, which is about one US quart more than a US gallon. I am not complaining but just wish I couls do better. Gas here is 69.4 cents a litre and it takes 4.54 litres to make an imperial gallon. I used to use a 3/4 ton 1968 Intrernational with a 304 engine and 4 speed std. trans and get about 15 MPG towing a 25 foot travel trailer.
Thanks for the responses.
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Lets see, one Imperial Gallon = 1.2 U.S. Gallons so you are getting 8.33 MPG. That sounds about right.
Cargo Master
Joined: Jul 2000
Posts: 2,281
Likes: 18
From: Northern California
fuel consumption
One of the most effective ways to change MPG is to change the gears. If you get a tach and read the freeway rpms and they are > 2800, you could change the gears or tires and get the rpms down to about 2200 or so.
On the FE a set of headers really helps the output because the stock exhaust is so poor.
Based on your post, I figure your paying more than $3 / gal of gas and if I were paying that, I'd switch to an RV cam, higher gears, headers, and cold air intake for starters.
On the FE a set of headers really helps the output because the stock exhaust is so poor.
Based on your post, I figure your paying more than $3 / gal of gas and if I were paying that, I'd switch to an RV cam, higher gears, headers, and cold air intake for starters.
Thread Starter
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New User
Joined: Jan 2001
Posts: 5
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fuel consumption
I haved a question about ignition timing. The initial timing with the engine idlinbg at 500 RPM and the vacuum advance disconnected is 10 degrees BTC. When I connect the vaccum advance at that speed there is no change in timing.
At 1500RPM with no load on the engine the timing with the vacuum advance connected was 33 degrees BTC. With the vacuum advance disconnected it was 25 degrees BTC.
Are these specifications correct?
The hose from the vacuum advance is connected to a pipe near the bottom left side of the carburetor.
I have also installed a viscous clutch type fan. Any ideas on the effect this may have on fuel consumption?
Thanks for all the responses
At 1500RPM with no load on the engine the timing with the vacuum advance connected was 33 degrees BTC. With the vacuum advance disconnected it was 25 degrees BTC.
Are these specifications correct?
The hose from the vacuum advance is connected to a pipe near the bottom left side of the carburetor.
I have also installed a viscous clutch type fan. Any ideas on the effect this may have on fuel consumption?
Thanks for all the responses
