My 289 is suffering from some serious blow-by... long and short is that I am weighing replacing it with a rebuilt version of the same or swapping out to a more modern fuel injected engine.

So I was wondering if anyone has any hard numbers for fuel efficiency of FI versus normally aspirated engines. say an EFI 5.0 liter versus carb'd 302.

tanks! (pun intended)

My wore out 302/2 bbl got 10-11 mpg everywhere. My EFI 5.0 gets about 13.5 mpg in town and a little better on the highway if I keep it under 70. It has about 2x the power and will only take another 3 years to finally pay for itself.

my son's 5.0 EFI in his 76 gets around 15 - 16 on the highway, not sure in town. The engine is old and tired too.

Its a brick sh*thouse. they wont get much better than what they ^ are. I'd be happy if it mine will get 10-12mpg. Better than my 79 at 7mpg

If you are at all concerned about MPG, sell the Bronco;)

No numbers to give you. Sorry.

thanks for the input! it's not that I am worried about mileage... so much as trying to make sure I understand what I may be missing. I was talking to a CJ-5 owner who told me he put a corvette crate engine in his CJ and it now averages over 20 mpg....on a bad day! So is it just stories or am I missing the boat??

if it's actually that much better than its something I should probably consider more. If not, then I'll just find a short block and call it good.

Cheers and Happy holidays!

The MPG isn't vastly different, although you will see an improvement. The main difference is driveability. It'll start quickly and not have issues with altitude. You won't have to mess around with a choke or tinker with jetting etc.

You want 20's for MPG's in a Bronco? Three letters...4BT (diesel swap)

But that's an expensive endeavor. Really, you'll be much happier in the end with a modern EFI engine...

Lurker here...except for Eric's stroker build, but had to chime in here. 302's in the 70's were lucky to get 12mpg... 289's in '67 and '68 handily reached 17-18mpg (I still have my mpg log from my first new '68 Bronco). Shorter stroke had everything to do with it (we're talking stock drivetrain, suspension, etc). Small Holley or Carter 4bbl back then with headers.

Verified by 8 other EB owners, verified odometer and GPS, my 351W with a Qjet got better mpg on every leg of a long trip than 5 other fuel injected EB's on a "Manly Man Run" to the Rubicon and back from Seattle, WA. I kept accurate records of every fill-up and mileage and averaged 14.5mpg on a 2,000 mile trip...including running the 'Con. There was two of us in the rig with 10 days worth of food, supplies, camping stuff, etc (heavy). I was running a ZF with 4.10 gears, 203, D20, 3 1/2" susp, 2" body lift with 35" BFG's at the time (did for over 10 yrs).

For mileage the best thing you can do is: narrow tires, lightwt rims, no suspension lift, no body lift, (HOLD IT, these recommendations aren't any FUN) bump compression to maximum amount for regular gas, dial in your distributor advance, good cam design, oh...drive slow. The HP needed to push your rig into a 70mph headwind compared to a 55mph headwind is amazing.

Done, sorry for the long post.

Do you CO guys have snow yet? Here at 6,000ft we have less than a foot... no fun wheeling yet!!!

Just wanted to update that I calculated my fuel mileage the last tank, which had some slow highway driving, some trail riding, and about 15 minutes of snow bashing. I was surprised to have gotten 14.8. I could probably get in the high teens going slow down a highway, but what fun is that?

nvrstuk - depends on where you look. The southern half of the state got nailed pretty good by a storm last week. Shut down i25 from Pueblo south. Alamosa has hardly any snow on the ground, but 15 miles away in Monte, there's 12" or so...

I have howell tbi and I get around 16 I have not checked since shorty headers and 2 to 1 exhaust but these things are gas hogs. I've heard of guys flashing or chipping it but your horsepower may suffer. I find when I use my left foot to drive I use less gas. Go figure

Thanks everyone for your input! I've been wondering about this for awhile. As a couple of you commented.. with more horsepower comes the likelihood of sticking ones foot into it more... I am definitely one of those!! Interesting to see the comment about 17-18 mpg from the older 289's.. that's close to what mine got before I started putting new things on the engine too. Now its 11 ..maybe 12.

hmmmm!!??

Not sure what I'll do, but certainly have a good spring project either way!

My old '74 with 302 3 speed 4.10 and 33's got 15.5 a couple of times on trips in the mountains. It had 4 bbl Holley as well. Until the motor got real tired it got pretty decent mileage. I don't even really have a feel for the 351W mileage in my current Bronco but it's probably 10 to 12 at best.

My EFI 351w gets 9.5-10.5. But I think a proper tune would diguo some hidden HP and MPG. It's the $900 bill to tune it that the B-itch. I wish I could find a shop that didn't want to make $700+ for 4 hours...