fuel mileage with 390??

Engine, ignition, fuel, cooling, exhaust

Moderators: Ranchero50, DuckRyder

Post Reply
User avatar
gregamorton
Blue Oval Fanatic
Blue Oval Fanatic
Posts: 935
Joined: Mon Jun 15, 2009 7:57 pm
Location: Blossom TX

fuel mileage with 390??

Post by gregamorton »

Guys just curious what fuel mileage you are getting with your 390 trucks? Mine is a 1971 crewcab 4 speed with 4.10s. I am looking for a 3.54 rearend as I dont need the low gears but here is what its getting.

1st tank ran half out and it got 8.2mpg

2nd tank ran it half out again but this time with new wires and coil and it got 10.2mpg

I dont like filling up the truck so I run it 4 days or so and fill it back up. Also with both tanks I averaged 55mph. I am hoping for 13-14mpg with 3.54s!!
1967 mercury F350 7.3 IDI ats turbo kit c6 gear vendor overdrive 3.73s rolling on 19.5s
1971 sport custom on 1979 f350 highboy frame 460 c6 np205 dana 60s 3.54s
1974 F100 baby blue & rust 240 3 speed 3.70s sitting on the ground!
1990 F250 extended cab FI460 e40d 3.55s daily driver
Possibly looking for my next bump right now!
Racer Z

Re: fuel mileage with 390??

Post by Racer Z »

I get 10 MPG Highway in my 70 F250. I've got a fresh 390 with C6 and a lumber rack. The 4-barrel carb is getting worn, needs to have the throttle shafts bushed. I've also using an Edelbrock Performer 390 intake with stock "log" exhaust manifolds.

Rear end gearing will effect MPG as will brakes and tires.
User avatar
Dirty Offio
New Member
New Member
Posts: 197
Joined: Tue Jan 12, 2010 11:46 pm
Location: Bellingham, WA
Contact:

Re: fuel mileage with 390??

Post by Dirty Offio »

my 68 Crewcab gets 14-16 running empty at 50-55 with 4.10's. (4x4)

BUT...

When I first bought it, it got 2 1/2 MPG. It had a tired old 360 (2 barrel) that needed a tune up, clutch slipping, with a 14' overhead camper (HEAVY).

Did the tune up (plugs, wires, cap, rotor, points, condenser, air filter) and changed the clutch. Bumped the mileage to 5.

Bought an electronic ignition conversion kit (Mallory Unilite), put it in and got 7 to 8 mpg.

Put a fresh 390 in (slightly warmed up) with an Edlebrock 4BBL and averaged 10. IF I keep my size 13 outta the secondaries! lol

All of the above was with the camper on it.

Pulled the camper out, and it runs 14-16 consistantly, provided I can hold the speed down. If I get up on the Interstate, the mileage drops to about 9.
When in doubt, hit the gas. It may not be the right answer, but at least it ends the suspense!!
The only substitute for Cubic Inches, is Cubic Money!
1967 F-100 swb "Varmit"
1968 F-250 4dr lwb "Beast"
1976 F-350 drw 460
1977 Club Wagon
1986 F-250 lwb
User avatar
fomocoguy
100% FORDified!
100% FORDified!
Posts: 1548
Joined: Mon Nov 12, 2007 10:04 pm
Location: St. Louis, MO

Re: fuel mileage with 390??

Post by fomocoguy »

Dirty Offio wrote:my 68 Crewcab gets 14-16 running empty at 50-55 with 4.10's. (4x4)

BUT...

When I first bought it, it got 2 1/2 MPG. It had a tired old 360 (2 barrel) that needed a tune up, clutch slipping, with a 14' overhead camper (HEAVY).

Did the tune up (plugs, wires, cap, rotor, points, condenser, air filter) and changed the clutch. Bumped the mileage to 5.

Bought an electronic ignition conversion kit (Mallory Unilite), put it in and got 7 to 8 mpg.

Put a fresh 390 in (slightly warmed up) with an Edlebrock 4BBL and averaged 10. IF I keep my size 13 outta the secondaries! lol

All of the above was with the camper on it.

Pulled the camper out, and it runs 14-16 consistantly, provided I can hold the speed down. If I get up on the Interstate, the mileage drops to about 9.
Just curious, what diameter tire are you running?
Joe

1971 F100 flareside 8ft
1964 Chrysler New Yorker Town and Country wagon
2006 Dodge Ram 2500 cummins
2005 Ford Ranger
User avatar
1972hiboy
100% FORDified!
100% FORDified!
Posts: 2421
Joined: Thu Sep 09, 2010 5:44 pm
Location: California, Santa Cruz

Re: fuel mileage with 390??

Post by 1972hiboy »

my 72 with 9.00x16's fresh 390 manual trans holley four bbl if I play nice with it, it will do the 10-12 mpg ballpark.....thats around town I dont have enough miles on the 390 to take it on long stints on the hwy yet...oh Ive got 4.11s
Rich
1973 f350 super c/s 460/c6 22k orig miles
1972 f350 srw crewcab special 390
1972 f250 4x4 sport custom 390fe Red
1972 f250 4x4 custom 360 FE " Ranger Ric"
1972 f250 4x4 custom 84k og miles 390
1971 f250 4x4 sport custom 56k og miles. 360
1970 f250 4x4 428 fe hp60 205 d60
Dont eat yellow snow.....
User avatar
Dirty Offio
New Member
New Member
Posts: 197
Joined: Tue Jan 12, 2010 11:46 pm
Location: Bellingham, WA
Contact:

Re: fuel mileage with 390??

Post by Dirty Offio »

fomocoguy wrote: Just curious, what diameter tire are you running?
Running 8.25 R16's. (35" tall) I have not run the milage since I put the 265 70R 16's on it. (it has been under the weather with fuel system problems for a while...but that is a seperate post! lol) I wish I could have found another set f those 8.25 R16 Continental's tho, they wore like iron! Still have them, and the tread is fine, but the sidewalls dry rotted out on them.
When in doubt, hit the gas. It may not be the right answer, but at least it ends the suspense!!
The only substitute for Cubic Inches, is Cubic Money!
1967 F-100 swb "Varmit"
1968 F-250 4dr lwb "Beast"
1976 F-350 drw 460
1977 Club Wagon
1986 F-250 lwb
User avatar
Dirty Offio
New Member
New Member
Posts: 197
Joined: Tue Jan 12, 2010 11:46 pm
Location: Bellingham, WA
Contact:

Re: fuel mileage with 390??

Post by Dirty Offio »

Update: I mistyped on my previous post. the tires are LT265/70R17, not 16. I have been running it around both local and interstate lately.

Local, running back and forth to work (10 miles, mostly 50 MPH road, several stoplights and stop signs, plus 2 roundabouts) it is running about 9 MPG.

running on the interstate at about 65, it is getting 13, so it cost me a couple of mpg to swap to the shorter tires.
When in doubt, hit the gas. It may not be the right answer, but at least it ends the suspense!!
The only substitute for Cubic Inches, is Cubic Money!
1967 F-100 swb "Varmit"
1968 F-250 4dr lwb "Beast"
1976 F-350 drw 460
1977 Club Wagon
1986 F-250 lwb
User avatar
woods
100% FORDified!
100% FORDified!
Posts: 2121
Joined: Sat Apr 02, 2011 10:34 am
Location: Washington

Re: fuel mileage with 390??

Post by woods »

In my 71 4X4 with 411's, 35's and a 428 I get close to 15. However, my engine is built a little "different" than the norm.
User avatar
390Nut
Blue Oval Guru
Blue Oval Guru
Posts: 1052
Joined: Sat Oct 16, 2004 1:23 pm
Location: Fife, WA

Re: fuel mileage with 390??

Post by 390Nut »

'69 f100 2wd, 390 running 9.5/1CR and a .270 Crower cam, bigger exhaust valves (CJ sized) with dual exhaust (stock manifolds) 4spd, 3.50 gears, was running 235/70R15's and got 10mpg on average. Got 31x10.5 tires on there now but haven't been driving the truck to know if the mileage changed.
Paul
Image
`69 F100 390 4spd driver
http://www.fordification.com/galleries/ ... ?cat=10251
Dura-Spark II Conversion info at:
http://home.comcast.net/~390nut/Dura-SparkII.htm

Pipes71 did once say, "bumps and bikes.. what a great combo!" :thup:
Racer Z

Re: fuel mileage with 390??

Post by Racer Z »

I recently took mine on a 200 mile day trip and got almost 12 MPG.

The spec are: 1970 F250 w/ 390 (fresh, stock) stock exhaust manifolds, Edelbrock Performer 390 intake manifold, Carter 4-barrel (needs work); 9.50 x 16.5 tires; auto; lumber rack. I had a couple of hundred pound of broken concrete in the bed, rode smooth. I sat on 65 MPH. With these tires my speedo is off by 7%, when it shows 70, I'm doing 65. The speedo registered 70 for the trip.

I don't remember if that was with dual mufflers or single. I changed over to single to make room for a camper special fuel tank.
Post Reply