Normal gas mileage?

[countryboytn]

I realize I'm driving a 2ton brick, with a v8.. but I still should get better than 6mpg shouldn't I? I'v calculated it more than once... and I average between 6 and 8 mpg

specs(for those who don't know/remember): '78 Bronco, 400,c6,3:55's (LS rear), with 33's. Has a 2barrel carb on it.

It doesn't seem to matter how I drive it either, flat on the floor... or like a grandma, I get the same.

 

[smokey]

When running right you should be getting closer to 12 mpg.

 

[1985 Ford F-150]

You talkin in town or highway. I can get almost 11 with mine 400 2bbl 4spd and 31s havent looked at the tag on the diff but id say probly the same gearing as well.

 

[countryboytn]

When running right you should be getting closer to 12 mpg.

That sounds more like it...

You talkin in town or highway. I can get almost 11 with mine 400 2bbl 4spd and 31s havent looked at the tag on the diff but id say probly the same gearing as well.

hmm... I wonder where I should even start? I know they put a carb on it back before we bought it, it doesn't load up or anything but I still wonder if it's setup right.

 

[greystreak92]

Check your on-car carb specs if the engine is tuned well. Even clean oil and new ignition parts won't help if the settings are off. Base timing might have shifted but usually that will be noticeable either with bogging down or knock.

 

[LEB Ben]

I recall highjacking another thread and discussing this with you a while ago...so it's been this way since you bought it, right? For reference, after I did the top end rebuild in my Bronco, I was/am capable of pulling 14mpg's on the highway and between 10-12 city depending on driving style. I have the same specs you do, except I'm riding on 35's and no LS and 4bbl Holley. Obviously the rebuild included new fluids and filters as well. It also included new plugs, plug wires and coil. Prior to the rebuild, I was pulling 7-9 city and about 10 hwy.


So if I had to predict the problem areas...I'd start with the carb, worn timing chain and probably old and worn ignition components.

 

[1985 Ford F-150]

Tyler yours aint full time 4wd is it?

 

[78freewheeler]

well ben your lucky i get 7.3 avg. and the only difference in motors is i run a xe cam

 

[countryboytn]

I recall highjacking another thread and discussing this with you a while ago...so it's been this way since you bought it, right? For reference, after I did the top end rebuild in my Bronco, I was/am capable of pulling 14mpg's on the highway and between 10-12 city depending on driving style. I have the same specs you do, except I'm riding on 35's and no LS and 4bbl Holley. Obviously the rebuild included new fluids and filters as well. It also included new plugs, plug wires and coil. Prior to the rebuild, I was pulling 7-9 city and about 10 hwy.


So if I had to predict the problem areas...I'd start with the carb, worn timing chain and probably old and worn ignition components.

I remember that, but figured I'd see if anybody had any advice, again.

It has been this way since I'v had it, and dad said he never got about 10MPG the whole time he owned it. With my slightly heavier right foot, it seems like it's getting about the same.

I spent $60+ in gas yesterday, to go wheelin' for 6ish hours...

how you like your 35's? I don't think I can run 'em without a lift but I'm more worried about power than anything.

Tyler yours aint full time 4wd is it?

Nope, sure ain't. I'm glad too.. I like playing in 2wd to much.

well ben your lucky i get 7.3 avg. and the only difference in motors is i run a xe cam

Sounds about the same as me.

 

[LEB Ben]

well ben your lucky i get 7.3 avg. and the only difference in motors is i run a xe cam

Holy bajeezus, that ain't much better than I get in Red, and she's got more power, 4.88's and 37" boggers.

how you like your 35's? I don't think I can run 'em without a lift but I'm more worried about power than anything.

Ehhh...the 35's are alright, I'm looking for more tire though. I'd like to go 6" Deaver's all the way around and get up on a 38...but it's all about time and money. The fellas over on FSB say 2.75" backspacing was the ticket to fitting 35" tires on a stock suspension. But I agree, I have 35's and 3.55's and I'd definitelty advise a regear.

 

[countryboytn]

So your saying, it MIGHT be possible to run them with the setup I have. even with minor rubbing, I wouldn't mind it much.

If I ran across a set for cheap, I'd probly grab them, for the simple fact that almost evertime I'v been stuck.. my axles where on the ground. Those extra couple inches would have helped more than once.

like this...

 

[LEB Ben]

Yes it is possible. Look up member Happster on on FSB and he's rolling 35's stock. The wheel well definitely looks stuffed, but word on the street is that there is bare minimum rubbing, and what rubbing there is is on the ra's and not the fenders.

 

[78freewheeler]

ben just curious how are you getting that king of mileage, ie carb cfm timing jets anything really to help get my mileage where i would like it a little better

 

[FordF-SuperDuty]

Yes it is possible. Look up member Happster on on FSB and he's rolling 35's stock. The wheel well definitely looks stuffed, but word on the street is that there is bare minimum rubbing, and what rubbing there is is on the ra's and not the fenders.

http://www.fullsizebronco.com/forum/showthread.php?t=158223

 

[countryboytn]

I LOVE how that truck sits... the 35's fill up the fender wells just about perfect if you ask me.

 

[LEB Ben]

ben just curious how are you getting that king of mileage, ie carb cfm timing jets anything really to help get my mileage where i would like it a little better

Carbs are Holley 650cfm vac. secondaries, electric choke. PN 80783-C. Beyond that, really nothing fancy. It was a basic top end rebuild with the DEH255 kit, new coil, new dizzy, new IM, super cooler rad. To be honest, with such a big jump from where I was to where I went afterwards, I'm not sure what did the most good. Coulda been eliminating vacuum leaks as well.

 

[Mil1ion]

see what you get if you keep the engine no higher than 2000 rpm in high gear ...while driving

 

[countryboytn]

I need a tach, I have no idea what rpms I'm turning. Honestly, it seems like alot though.

 

[1985 Ford F-150]

Well I can give ya a ballpark with 33s, 3.54s and a 4 speed in my 86 it turns 2000 at 60 so your probly pretty close to that.

 

[greystreak92]

The math to calculate it isn't tough.

MPH (usually a highway speed of 60) X rear axle ratio (typically 3.55 in a stock Bronco) X 336 (constant) / 29.5 (actual diameter of the tires you are running (not the nominal dimension...31's are only about 29.5-29.75" in diameter. The same is true for bigger tires. If you are unsure or don't believe me, measure from center of the hub to the pavement then double it.)

Short version

60 x 3.55 x 336 / 29.5 = 2,426 RPM (in highest gear @ 60 MPH)

Just plug in your own numbers based on your truck. If your truck has overdrive you will need to multiply by the overdrive gear ratio as well BEFORE multiplying by 336.