Well I have see some people claim got 17-23 mpg out 90's bronco with 5.0L/ AOD plus gear ratio 3.55.

I am curious how they do.


I am make this thread so I would be happy if everybody post what mpg and how they did to improve mpg like 10 to 12 or 15 to 17 mpg how?


Please list years, engines spec, transmission model, gear ratio in axle, tires size, weight, and what was speed that you got good mpg like 55 or 70 mph.


here example
79 F150 custom 4wd with 300 4.9L, 4 speed np435, 3.55 in axle, 31x10.50x15, 5,200 pounds, and speed at 60 mph I get 17-21 mpg depend.

 

Mileage can be increased greatly by putting the 1990 Bronco (DonKo) on the back of a flatbed tow truck and counting the miles traveled thusly in the mileage calculations. Some don't agree with this technique, but it works that way for others.

 

My '83 Bronco averages 20-23 mpg every week. Keep in mind, I mainly use secondary roads where I can stay in high gear at 45-50 mph.
First thing I did was rebuild a 1995 300 inline 6 for the truck, cranking compression is 175psi on this motor, and it still has the "fast burn" fuelie head on it. I retained the f/i dual exhaust manifolds, and they run into a 3" exhaust with flowmaster, to drop back pressure to as close to zero as I could get it. I have the exhaust exit under the passenger door, perpendicular to the flow of air as the truck moves. (A slight venturi effect to assist exhaust flow? It was worth a try)



I installed a '72 intake manifold with 1 bbl carb. I'm also running a rebuilt points distributor, and as much timing advance as it will tolerate, since I don't use this truck for towing, only commuting to work. The timing is actually on the ragged edge, and if I tried to pull a trailer it would likely ping really bad. It also cranks hard on hot days, due to the high initial timing. I experimented with it for a couple weeks to get the best setting for mileage. (With the fast burn head design, the timing requirement is far lower than the older 300s) When I rebuilt the 1 bbl, I modified it with parts from a couple other carbs. No details on that. Working with carbs for 20 years has its advantages.
I use the '95 serpentine belt setup, but I deleted the smog pump, so the belt is a weird size. Since the f/i '95 block doesn't have the fuel pump hole, I had to cut a hole to use stock mech. pump. (the '95 cams still have a pump accentric, and the block mounting boss was drilled already for the pump, just had no access hole)
I wanted to use the 5-speed from the '95 parts truck. I installed the stock '95 hydraulic clutch system, but I had to fabricate a bracket so I could use the '95 pedal assembly in the '83 truck.
Gears are stock 3.55s, tires are stock with low tread on them and max air pressure. (new tire treads will get worse fuel mileage than worn ones) I tried a set of 16" jeep wheels with taller narrow tires, and mileage increased slightly on the highway, but decreased slightly around town, so it's not worth the bother.

 

The only way to beat a 300's fuel mileage is to drop in one of these. So that's what I'm currently doing with my '78 Bronco. I expect at least 25 mpg. And maybe just a little more acceleration. heh

 

That is one tight fit for a cummins, how much clearance do you have at the firewall for that cummins.

The best mpg on my 91 that I ever got was 13 mpg. That was on the current 351, with the C-6, 3.55 gears, a worn set of 31" BFG ATs, on back country roads doing 55 to 60 mph all on one 2 hour trip in the middle of summer, and use to be a 3 inch aftermarket Y pipe (dont know who made it but it looks similar to the bassaini y pipe) going into an old rusty flowmaster split into dual 2.25" pipes. When i went to a set of 33" without changing a thing on the truck. The mileage has dropped to 9 mpg with all city driving with 70 mph as the top speed and no change to the drive train, but now the dynomax single 2.5" out pipe (the flowmaster rusted to pieces on me).

 

Check out the mileage tracking results I posted in here a while ago.

https://www.ford-trucks.com/forums/8...g-results.html

 

I like (and heartily agree with) g_k50" suggestion! But mine would be, improve air flow... there isn't an OEM engine setup that can't be improved upon at least a little bit in this area. Any engine that breathes better should work more efficiently.

 

Why not 4bt? It smaller and little light than 6bt. 4bt could get like 25-35 mpg if you do right.

 

There's actually more room in the Bronco than there was in the Dodge parts truck, due to the deep indentation in the firewall. I wanted the motor set back as far as possible mostly to get the weight off the nose, but also to clear the stock front crossmember, which it did. (It ended up being 3.5" further back than the stock V8)
The stock downpipe from the Dodge is a perfect fit in the Bronco:

As the pic shows, there's plenty of room for even an aftermarket 5" downpipe.

For fitment purposes, I'd put the stock adapter back on and taken pics.

Plenty of room here! (I love body lifts)
This truck is a dream to work on. I can almost stand between the engine and the frame rails, and it's so tall, I can sit comfortably under it when I work on it. Who needs a jack?? ha

 

I paid -$200(that's negative 200) for the 6BT, that's the biggest reason. But I also prefer the sound of the 6BT plus I want to build close to 1000 ft/lbs eventually, and it's a lot easier with a 6. There is the uniqueness factor as well.
The consensus is that this truck will get 25-30 mpg, due to the light weight and high gearing. I'm expecting at least 25 mpg, anyway, if it's higher, it's a bonus.

The 6BT weighs 1000 lbs fully dressed, the 4BT weighs 700 lbs. A 460 weighs 750 lbs, the stock 400 that came in the truck weighs 700 lbs. Using this data as a reference, you can imagine how much weight is actually placed on the front spring when the 6BT is moved rearward 3 1/2". The front of the Bronco only dropped 1 or 1.5 inches when the motor was set in it.
Compare:

With no engine.


With 1000 lb Cummins engine.

Since people often put plows on their F150s and Broncos, I'm not concerned much about the weight of this motor. A plow puts what, 400 lbs way out in front of the truck??

 

Looks pretty level to me

 

cant wait to put one of those into my 78 bronco, but not for mileage.

 

1989 ford bronco xlt 5.0, aod trans, 8.8 rear, 31" tires on 15" rims, 129,950 miles

i get somewhere between 10-14 anywhere i go. replaced the fuel filter and oil not long ago, compression is great all across, some blow by in the oil cap, slight miss somewhere. mismatched plug wires.

tore it all down 4 years ago to do crank/cam bearings and all of the seals. all new gaskets too. all new fluids. tires have only 6,000 miles on them since new....

why is my milage so poor? timing gear is metal, not plastic one.

exhaust fumes are outragous too

 

302s don't get very good mileage in a truck. The 302 I pulled from my Bronco was averaging 8-10mpg, it was a 4bbl 250hp motor, with 44k miles on the rebuild.

 

my buddy advanced the timing like 10 degrees from center and he said the f-150 with the 302 (1994) gets 18 highway now.

does the timing trick work on these without sacraficing alot of horsepower?