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Discussion Starter #1
there has to be a way to get better gas milegage out of my 78 bronco short of dropping a 4 banger. the engine is pretty much stock except for the twelve year old rebuild that from what i was told was a mild one. i was just wondering if anyone was able to give me some info or help or point me in the right direction. by the way i love this sight it has given a lot of inspiration and info on how to work on my bronco right the first time. there are some very dedicated and professional people here. thanks for everything and i look forward to more and any i help i can give know or in the future. thanks mike m
 

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tire size? gears?
 

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It's a 6000lb barn door goin down the road. It won't be that good. I'm lucky to see 10mpg. Best I've ever seen is 13mpg goin down the highway.
 

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Thanks 351w500
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Ya It all depends on what you opinion of GOOD gas mileage is. Im very happy with the 12 mpg I get up here at 5500 ft 9mpg when Im towing the work trailer which is almost daily but it 6 to 7 thou lbs heavy. When I drive it down below 1000 ft elevation I get 15mpg+. Now this is with 35" tires and 4.56 gears after I put the lift on I lost 2 mpg on mileage.

Its all going to depend on how you drive it and how it is running.
 

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Have you guys heard of this performance tip by FSB members Sweiv or Sixlitre where you can increase the plug gap and bump up the timing for better gas mileage and a bit more powerrange?

A lot depends on what engines you have in your Bronco's, ie: 302 or 351 preferably with Fuel Injected vehicles but in any case the theory should work with any engine, Carbed or FI, it's an old Hot Rodders trick.

Check it out!

Thread: ignition and timing upgrade...

Good Luck ~ :thumbup
 

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Discussion Starter #8
after today it will be driving on 31x1050 r15's with a new front end rebuild.a new tune up on a 351m with stock 2 barrell carb which i will probably try and rebuild here soon. but i will try anything onece, twice if i like it. so im going to investigate and i will share my information with you. i will get to you all. there has got to be a better way.. there has got to be like an ancient star trek secret.
 

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I hope to get better than my 7 to 8 mpg with mine? Your driving a bronco not a 2wd pickup what do you want more than 13 that's great mpg
 

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To do justice to the "ignition and timing upgrade" performance tip, you do need all new ignition components including a 48K volt coil and in that way you get the maximum benefit....I use 9mm FMSR wires with MSD ignition components but there are less expensive components available as well....

Having the Carburetor in tip top shape is also another benefit along with good working throttle linkage so there's binding helps bring up the MPG's..

It's worth a try IMO, everybody here swears by this upgrade!

Good Luck ~ :thumbup
 

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After messing with my 400 for years and never getting better then 7-8mpg I built up a 460 and threw it in. My 460 has 3 times the Hp and 4 times the TQ and my mileage jumped to 10-12mpg. No one will ever convince me those 351m/400 motor are any good.

Both my 400 and 460 have similar mods I just truly believe the stock motors are garbage and do not respond well to mods. Now all the 351m/400 lovers will jump on me and show links to 500HP M/400 motors but I don't care. It's far easier to get power and milage out of a 460 IMO.
 

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shouldnt buy a Bronco if you care about about mileage. most 4x4 will not yield DD MPG.
 

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Replace the retarded smog timing set with a straight up (0*) set.
A good valve grind helps.
Headers and a dual exhausr.
Check the fuel pressure and float level in the carb, replace the needle and seat.
 

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do the sixlitre tune. remember the crucial parts are the wires, plugs, cap/rotor. stay away from msd. autolite/motorcraft coppers work best for plugs. the taylor spiropros are good but our engineer sig recommends the autolite professionals. a new stock coil will help a bit and just whatever brass cap and rotor you can get. personally im gonna try out a taylor cap and rotor since the price is awesome. its all outlined in the sixlitre discussion thread.

http://www.fullsizebronco.com/forum/showthread.php?t=63592&page=82

weve discussed these things in the last few pages.
 

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I'm going through the same process now, trying to trim gas mileage... and am getting stumped.

Gas mileage is a crap shoot in these trucks IMO.

I have a 400, 205, 4:10s and stock tires on my F250 and get 15 to 16mpg(highway)
I have a 400, 205, 4:10s and 33s on the bronc and get 6.5 to 7mpg(highway)

Same carb both, tuned the same, driven the same, on the same route/roads. The bronc should be slightly higher geared with the 33s calculated in, and its lighter....

Driving me nuts!

G.
 
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