[BFix] Thinking outload gas mileage and EB.... LONG now!!

Wed May 7 22:39:36 MST 2008

Just what Eric said...

  I've kept extremely detailed mileage logs on all my myriad of tire/wheel/engine/suspension/body lift combinations for 32years of driving my Bronco this JUNE. Wow, 32 years I've owned "it", well parts of the orginal anyway.  Before that, my Dad kept super accurate mpg logs on his '69 (that's where I got it from)     :)

Anyway, 17 mpg with Eric's combination is spot on. That's what we used to get towing our 600lb Apache tent trailer with the alum boat on it. Go a bit slower (like back in the FIRST oil crisis) when our National speed limit was 55mph and our freakin' Gov'nr Dixie Lee Ray had Washington speed limits at 50 mph. Now that's crawling when going from Ellensburg to Spokane since there's only about 1 exit every 30 miles or so... but anyway... I could average 18-19 everyday when traveling 50 - 55 mpg. 19-20 on extended trips (like Eburg to Spokane).  289, headers 4bbl, 3 spd, 28" tall L70x15" tires, 3.5 gears, etc

289 avgs 2-3 mpg better than any of the 3 different 302's I've ever run.  My Dad's 69 w/stk 302, 2bbl & 4 bbl, 3.5 gears, headers & stock manifolds and G78x15" Town and Country tires always got 15mpg (but he had a big pwr difference with the perf upgrades. 14mpg towing  He put 186,000 miles on it from brand new to when he sold it and always got the same mileage! 

My first 302 in a smog ridden '77 got a lousy 11mpg, stock 3.5 gears, C4. I hated that trans. lol   I tried 4bbls and headers and bumped it up to 12mpg. What a PIG. Terrible performance also. Engine was in good shape, low miles, just a smog motor/low compr. Could barely tow a small trailer up a long hill, when it did, it got 10mpg. I stole all the running gear out of this one and still use the housings today.

My next 289 was an HP289/271horsepower solid lift cam factory motor. Numbers matched till I got rid of the heads. (Iknow, what a fool) Anyway, it ran like a bat out of h#ll and I still got 16-17 mpg. I broke a lot of parts wheeling in that rig. Couldn't keep my foot out of it.  :)  3.5 gears, 28-30" tall tires. 3spd

First bump up to 4.10's with a 289 4bbl/headers cam 3 spd still got me 15-16 mpg

Next bump up to 4.10's with a 289 4bbl/headers and a 4spd O/D toploader style Granada trans got me16 -17mpg

Couldn't stand the tranny so I went with a true toploader 4spd out of a Torino, with my HP 289/271 HP engine with description above. Still got 16+ mph but started twisting a LOT of rear axle shaft splines off btw 1st and 2nd gear shifts (hmm...can't understand how that always happened)  lol

Rolled this rig and stuffed in my 351/headers/cam/4bbl (Holley/Carter/Q-jet) block that I still have today. 4.10 gears (now 4.56), started with 32" tall tires now have 37". Stock suspension with the 33x9.50 tires and 15mpg dropping to 12-13 mpg today with 37"s, 2" body lift and 3.5" susp. 14.5mpg to the Rubicon and back with above 351W with 35"BFG's (40,000+ miles of gas tests with 35" tires) running 3.5" susp and 2" body. Often at 70-85+speeds ask Eric  :)

I noticed a big difference when adding the susp and body lift. Handling suffered, brake dive really increased, pwr at freeway speeds was reduced (wind resistance).

Sorry if this took forever, I've run SO many combinations of all the above that it would take quite the Excel spreadsheet to show it all.

Best mileage?  Keep stock lift ht, run a 289 (fuel inj), skinny tires/stock size, 3.5 gears, 4 spd toploader (less friction losses than autos), O/D won't do you much good with 3.5 gears and small cubes pushing a small brick at freeway speeds.

Or buy a loaded one owner 91 Civic (even has cruise control) for cheeeap  HA

Lot's of possibilities but they all cost money that'll you'll probably NEVER earn back in savings in fuel costs unless you keep your rig for 30+ years like me.

Brian @ Columbia River Broncos...20 forward gears & 4 reverse to choose from.
  ----- Original Message ----- 
  From: Eric Neasham 
  To: mail at broncofix.com 
  Sent: Wednesday, May 07, 2008 7:59 PM
  Subject: Re: [BFix] Thinking outload gas mileage and EB....

  Well,

      My EB, with the stock 3 speed, 289 (stock bore), 4.11 gears, 31x10.50 15 tires, stock suspension towing a 1000 lb utility trail would routinely get 17 MPG to and from SOB - about 5 hour drive...

     I think the height of the EB has more to do with the mileage, and a 289 usually gets better fuel economy over a 302 with the rest of the EB being the same... if you don't believe me, ask Brian Cooke... wh has run them all.. and ZF...

  just throwing more fuel on the fire...

  Eric
    ----- Original Message ----- 
    From: Jim Lemanek 
    To: mail at broncofix.com 
    Sent: Wednesday, May 07, 2008 11:21 PM
    Subject: [BFix] Thinking outload gas mileage and EB....

    Reading all that we do, it looks like someone with a 5.0 and an OD tranny like a ZF gets maybe 18 mpg.  What gears is that with?

    So if I were to keep the 3.50 gears, install a 5.0 and a ZF, any guess what I could get?

    According to gear calcs, an OD at .75 and 34" tires, at 70 mph I get 18XX rpm at 70 with 3.5 gears and 21XX rpm with 4.11.

    What do you think that would do to mpg? Stock 92 mustang 5.0.

    Just wondering thoughts.  I was gonna ask best mpg setup as an excercise but quickly realized I would get a discussion on 4bt probably.  Thats a bit outside my motivation based on my current resources.

    --Jim

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