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Old 01/19/08, 08:30 PM   #1
DEEPWOODS
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Gas Mileage?

I have a 75 bronco with a 5.0 mustang engine, rebuilt engine cam edelbrock intake and carb. headers 350 gears 32" tires c4 trans. i only get 8 mpg.My wifes 98 mountaineer with 5.0 engine and AOD gets 20 mpg. Will fuel injection and a AOD help me?, i am told only about 1 mpg for fuel injection and maybe 2 mpg with AOD trans. Can any of you that has fuel injection and AOD setup tell me what you get Thanks Keith
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Old 01/19/08, 09:03 PM   #2
Deezel_dusten
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Quote:
Originally Posted by DEEPWOODS View Post
I have a 75 bronco with a 5.0 mustang engine, rebuilt engine cam edelbrock intake and carb. headers 350 gears 32" tires c4 trans. i only get 8 mpg.My wifes 98 mountaineer with 5.0 engine and AOD gets 20 mpg. Will fuel injection and a AOD help me?, i am told only about 1 mpg for fuel injection and maybe 2 mpg with AOD trans. Can any of you that has fuel injection and AOD setup tell me what you get Thanks Keith
i am guessing you have some tuning issues with the carb you have. How many CFM is it?
I was running a 302, with 4.11's, 35's, a mild cam, stock intake and a Q-jet carb and was pulling down 16 freeway 13 city.

1974 Bronco Wild Horse 4.5" Rock Crawler lift, Fenders Cut, d44(open)/9"(LS) 4.11's, 351W/C4/D20, 35" BFG's, JD Twin stick, Warn XD9000i.
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Old 01/19/08, 09:29 PM   #3
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Sounds Like Me! I have a roller 302, GT-40 P Heads, Edelbrock RPM Air Gap Intake, Holley 470 Truck Avenger, C-4, 3.55, 33's and my first Gas Mileage Calculations were around 6 MPG! Grant it alot of that time was tuning, in my driveway, Full Throttle Runs trying to tune it! Hopefully mine gets better now that it is tuned!!
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Old 01/19/08, 10:32 PM   #4
localrich
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I'm hand calculating 8 mpg also

Rebuilt 302 with a weiled intake, edelcrap carb, headers, dual exhaust, 4.10 and 32's

66 EB in the works
72 EB Sport
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Old 01/19/08, 11:12 PM   #5
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13-15 at 75mph depending on what direction the wind is blowing. get a little better at lower speeds. You should be able to pull more out of it than 8mpg stock they got about 12mpg. Check the jetting on your carb and it might be a good idea to get your dist curved so that all the advance is in before 3000 rpm, If that dont help you then you either need a camshaft that is matched to your vehicle(ie gearing and driving needs) or the tranny is slipping bad. And with 32in tires and 3.50 gears your calculations are probably off unless you have changed the drive gear for the speedo. So you might gain a mile or two just off off that.

73 Ranger 2 1/2 lift 302 TFS heads NP435,PS,PDB, tierod over, 33x10.50x15 BFG M/T
71 Sport 63,000 miles all orginal except for cut fenders 302 3sp 4.11's D44/BBTrac lok rear
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Old 01/19/08, 11:13 PM   #6
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i'm getting between 12 and 14 highway, about 9 or 10 in town. holley 470TA, nv3550, 4.10's, 33's. depends if i can keep my foot out of the fan...

i know someone running an AOD with a EFI 5.0, 35's, and 4.56's. he's getting about 16 in town. yes, EFI and AOD will make a difference. i know a girl running 4.10's with 31's, a 5.0 EFI, and a 3 speed, she claims about 18 highway. IMO, edelbrock carbs suck for mileage!

from the factory they were only rated at 9.6 mpg.
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Old 01/20/08, 08:07 AM   #7
Broncobowsher
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Quote:
Originally Posted by DEEPWOODS View Post
I have a 75 bronco with a 5.0 mustang engine, rebuilt engine cam edelbrock intake and carb. headers 350 gears 32" tires c4 trans. i only get 8 mpg.My wifes 98 mountaineer with 5.0 engine and AOD gets 20 mpg. Will fuel injection and a AOD help me?, i am told only about 1 mpg for fuel injection and maybe 2 mpg with AOD trans. Can any of you that has fuel injection and AOD setup tell me what you get Thanks Keith
EFI could help some if the existing tune is really jacked up.
In your case the AOD would probably hurt mileage more then anything else.

One thing I notice is 32" tires and 3.50 gears. It is possible that the factory torque convertor has too high of a stall for that combonation. The convertor may be doing a lot of slipping at cruise speed and eating fuel economy. You could very possibly get better mileage with a set of lower gears. Particurly since you have a performance based engine that may not be efficient at low speeds. But a low stall convertor will not be matched very well for the performance parts you have in the engine.

Anyway it is almost impossible to tell why a particular vehicle is getting bad mileage over the internet. There are way too many variables. We can all throw out guesses. But a realistic mileage to get out of an early Bronco is low teens. 12-14 is the typical range.

"She's built like a steakhouse but she handles like a bistro"-Zapp Brannigan
“How hard can it be?”-Clarksonius 4th century BC.
Full throttle, it either solves the problem or ends the suspense.
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Old 01/20/08, 09:18 AM   #8
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I have a 302, with performer 289 intake, and edelbrock carb, not sure of anything else, because the work was done by PO. But with 33s, 3.50, and a 3spd, I only get 8 mpg also. I was a little disappointed by this also, I thought I would at least get 10 mpg.
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Old 01/20/08, 09:52 AM   #9
67horse
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I dont feel so bad now im getting about 8-9 MPG with a 351W 33" tires 411 gears a holley 650 Truck avenger carb and a lumpy cam. I would really like to increase my fuel mileage so I can drive it more. 33 cents a mile is just a little steep.
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Old 01/20/08, 10:29 AM   #10
broncnaz
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No matter 302 or 351 if you have the proper camshaft for your overall gearing you should be able to pull more than 10MPG 12-15 should be easily obtainable for most people with small lifts and 33in or smaller tires.
Most of your mileage increase will be with the correct camshaft the rest will be gained by correct timing and jetting.

73 Ranger 2 1/2 lift 302 TFS heads NP435,PS,PDB, tierod over, 33x10.50x15 BFG M/T
71 Sport 63,000 miles all orginal except for cut fenders 302 3sp 4.11's D44/BBTrac lok rear
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Old 01/20/08, 10:52 AM   #11
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I have a fresh 302, .030 over, performer cam, intake, edelbrock 650 carb, msd dizzy and coil, stock 3.50 gears, 3spd, and 31's, as near as I can tell I get around 10-12MPG. I haven't really tuned it very well, the carb could use larger rods, and the timing advance it straight out of the box, and could probably be tuned better. I know a couple of stock 5.0s with AOD's 35's and 4.56's supposedly getting 16-17 MPG, on the highway. I don't know how they drive, nor have I verified there milage, but this is some of the best early bronco milage I've heard of.
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Old 01/21/08, 07:09 AM   #12
commoncold
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I'm worst of all here, when I had to bring my bronco back from the mechanic (10 miles) I put in about 2 gallons and it ran out of gas before I got home . I have a 351W with 36" tires, I believe camshaft only has 15,000 miles on it- you don't need to worry my friend, as long as you get better mileage than 4.5 mpg
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Old 01/21/08, 12:16 PM   #13
Deezel_dusten
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These stories to me are all proof of improper tuning, or setups. I stated before that carb tuning and cam selection make the difference.
My old setup was
302 with 289 heads, stock intake, q-jet carb, crane 272 cam, headers, and dueal exhaust. C4, with 35" tires and 4.11's. It would easily knock out 16.5MPG at 65, and 13-14 in town.
My new setup which is a crate 351W, headers, stock intake, q-jet, and same drivetrain is getting 12mpg intown and 14.5 on the highway at 65mph(~2500rpms)
It has plenty of power to do anything i ask it to also

1974 Bronco Wild Horse 4.5" Rock Crawler lift, Fenders Cut, d44(open)/9"(LS) 4.11's, 351W/C4/D20, 35" BFG's, JD Twin stick, Warn XD9000i.
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Old 01/21/08, 01:11 PM   #14
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I don't know about the rest of you, but I am not restoring my Bronco with gas mileage in mind. Not even part of the equation. If I was worried about mileage, I'd buy a Prius. Of course, this is not to be a daily driver for me. This is my play around on Saturday, drive to work once in a while, vehicle (if it ever gets on the road that is).

Just an FYI, I own a 2004 Xterra. You want to talk about a surprise regarding mileage. I was silly and believed the window sticker (say about 19 - 20 highway). Other cars I have bought were very close to the sticker mileage rating. The Xterra gets 15 - 17 highway, depending on how heavy my foot is. Thing is, its anemic V6 has so little power for such a heavy boxy truck, it makes me put the foot down most of the time. I tried a cool air intake and different exhaust and maybe it made 1 mpg difference. Not much else I can do to it probably. I just live with it. My 96 Dodge Ram 1500 4x4 get 15mpg and it gets that when I drive the snot out of it or not. It is pretty much stock except that I modified the throttle body like they sell on Hughes Engines (I own a milling machine) http://www.hughesengines.com/general...icleID=1000001.
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Old 01/21/08, 02:14 PM   #15
76Broncofromhell
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My guess is timing and carburetor jetting. I think you have too little advance too late in the RPM range coupled with way too much fuel in the mixture.

My 408W occasionally flirts with double digit fuel economy readings. I would strongly recommend re-curving your distributor to get full advance ~ 2500-3000 RPM and to run your total advance around 36-38*. That should solve most of the fuel economy problems.

Most guys ignore ignition timing for some reason, assuming that distributors are plug and play, which they are not.

'70 Bronco - 408W
'45 Ford GPW - 351W
'84 Toyota - 5.0L HO
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