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make my '74 jeep more of a fuel miser-thoughts?

Discussion in 'Intermediate CJ-5/6/7/8' started by joe28, Feb 4, 2011.

  1. Feb 4, 2011
    joe28

    joe28 Member

    North Eastern Pa.
    Joined:
    Oct 21, 2009
    Messages:
    170
    Let's face it. Fuel prices are climbing higher than my blood pressure!chainsawguy
    I won't be long before it's $5 forever.
    I've desided last spring this is my LAST jeep project. 18 jeeps in 40 years is enough.
    So that being said I went into this '74 with the idea of running it til my kids take my keys off me.
    Fiberglass body, metal Meyers top, but everything else is OEM including the bench seat and steering wheel.:)
    Seems my little blue 232 I-6 doesn't like regular fuel with the 10% ethonal, (I get like 12mpg), but it's happier with a better grade (17 mpg on high test, but the cost...)
    It's all stock in the motor 45,000 easy miles on it (well there is a turbo muffler on it to make it growl)
    I've got the EGR unhooked, the vac advance (yep points), hooked to the carb instead of the thermo switch.
    I've bumped up the timing 8 degrees, leaned the idle mixture down til the motor has a "twitch".
    So I THINK I've done all the cheap stuff.
    I've added 2" soft ride springs and have 225/15 aggressive tires on it.
    next idea...................
    Taller RADIAL tires (easier ride on my old bones), to change the gears ratio to the ground, (slow the RPM down. I do maybe 4500 at 60mph).
    Anybody tried a Webber carb instead the the 1 bbl carb on it now???
    How about a nice header, intake system to breath easier??
    I was gonna try, (I shouldn't say "was" I AM gonna. My son has to do a motor at trade school next year), a 4.0 or?????? motor and a nice intake/exhaust sytem, just cuz, no other reason.bunny with a pancake
    Any ideas to make this 'ol girl cheaper to run???? (I'd try making it "Fred Flintstone powered, but I don't think I can push it much with my legs though the floor)!R)
    I'd hate to have to sell it cuz of the cost of gas, but a Subie Baja is looking better and better.
    Joe
    Once you get the "jeep itch" it never goes away. I've heard of guys selling thier kids, pimping thier wives to buy goodies for thier jeep!R)
     
    Last edited: Feb 4, 2011
  2. Feb 4, 2011
    pathkiller

    pathkiller Member

    Lorton, VA
    Joined:
    Apr 17, 2005
    Messages:
    878
    A carb swap or engine swap will not improve mileage. Your 232 should be getting much better than 12mpg. If you've seen that original road test someone posted a while back of a new 74 CJ5 with a 232 it was getting somewhere north of 20mpg in their testing. Why did you unhook the EGR? It's actually beneficial and will improve mileage if it's functioning properly. It reduces combustion chamber temperatures, allowing for a leaner condition.

    I would consider an ignition upgrade, either a Pertonix setup to get rid of the points, or a drop-in HEI type of distributor. A hotter spark should improve efficiency as well.

    Do the math of the tradeoff between MPG and cost for using a higher grade fuel. A jump from 12 to 17 mpg is huge, a 42% increase in fuel consumption. Let's say regular grade gasoline is $3.00/gal. That means you could pay up to $4.26/gal for premium and still be saving money over using the cheap stuff and suffering poor consumption. Around here even the highest octane premium is only around $3.50/gal, or only 16% more than regular. Meaning you're still saving 26% by using the premium fuel and getting better mileage.
     
    Ol Fogie likes this.
  3. Feb 4, 2011
    Rick

    Rick Member

    Hanson,Ma.
    Joined:
    Oct 19, 2006
    Messages:
    287
    "I do maybe 4500 at 60mph".

    I would think this would be a major cause of poor fuel economy. Do you know what gear ratio you are running? Also, don't see why running premium would make that much of a difference.
     
    Last edited: Feb 4, 2011
  4. Feb 4, 2011
    Ghetto Fab.

    Ghetto Fab. Member

    Atascadero, Ca.
    Joined:
    Jan 13, 2005
    Messages:
    512
    I don't think I've even gotten to 4000rpm with any one of my vehicles, well maybe. Thats definately not cruising rpm.

    Thinner less aggressive tires do better for mpg. Also, remove as much weight as possible.

    Kevo
     
  5. Feb 4, 2011
    OleBlue

    OleBlue Sponsor

    Tennessee
    Joined:
    Feb 14, 2010
    Messages:
    1,001
    Any of you running a stock 304, t15, 3.73 rear-end, and 31 inch tires? If so, what mpg are you averaging?
    Posted via Mobile Device
     
  6. Feb 4, 2011
    timgr

    timgr We stand on the shoulders of giants. 2022 Sponsor

    Medford Mass USA
    Joined:
    Aug 10, 2003
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    23,596
    No, you can't be doing 4500 at 60. If you have the short original tires and the optional 4.27:1 axle ratio, you'll be doing about 3000 RPM. It may sound like 4500, but it's not.

    The original carburetor will give you as good a mileage as you can expect with a carburetor.

    If you have taller tires than stock, then you are going faster than the indicated speed ...

    My new '73 304 with 4.27s and 31s got, at worst, about 12 mpg. And I drove it at California highway speeds (even in the '70s, 65-70 was the norm). My '75 CJ-6 with a 258, 3.73s and a full hard top got 14 easily, that on a 50 mile freeway commute from Santa Monica to Irvine.

    I suspect you have something wrong in your engine tuning. What do your plugs look like?
     
    Last edited: Feb 4, 2011
  7. Feb 4, 2011
    joe28

    joe28 Member

    North Eastern Pa.
    Joined:
    Oct 21, 2009
    Messages:
    170
    Plugs look good, complete tune up 2000 miles ago. The compression is good, cylinder leak down good. I used a vac gauge when set it up, so it looks good. I've been spinning wrenches for a living since, well since Nixon was "the man" so it's not new sheet to me...........:rofl:
    I'm thinking (not looking at the shop manual) I have the stock gearing in my differntals 3:73??????
    I have a Pro Meter tack mounted on my steering colum, Although used, I think it may read good, it show good idle rpm (750) as my the tack/dwell meter. (although when it's cold, it shows my motor turning at 8000 RPM)!
    I removed the EGR valve, to increase the rpm.
    Exgaust gases cool the cylinder, but it does take up some space where a air/fuel charge would be.
    The EGR stops pinging, by lowering the cylinder temp.
    Shade mechanic set up, keep advancing the timoing til it pings or is hard to crank hot. Best way set the engine speed to 1/2 way, turn your dist to highest rpm, and try it.
    The points system works well, (I repalced the bushing in the dist, sleeved the mechaincal weights, got new springs. I'd bet this works as well as any electronic set up. Dwell stays solid through out the rpm range.
    I have a Excel coil to "juice" the spark, (it's cool to see the difference on the Icelliscope)!
    I thought I get more MPG than this, but............
    I'm wondering the ethonal mix in the engine, (my '91 Harley Electra has dropped some MPG last summer using the ethanal mix. When you own a bike for 20 years you KNOW the mileage you get).
    I've had pretty decent luck dropping Holley carbs on some older engines in power and mph, (hence the Webber swap).
    In winter you get a lower MPG due to the mix they add to the fuel, choke time, (I have a manual choke on this carb).
    back in '74 regular gas was 95?? octane, (today it's 89), hence the high test try.
    Joe
    What to do? What to do? What I'll do is gt another beer and divine inspritation will come to me!:beer:
     
  8. Feb 4, 2011
    '74Renegade

    '74Renegade Active Member

    Fair Oaks, CA
    Joined:
    Sep 1, 2005
    Messages:
    1,275
    15 MPG was the best i have gotten with this set up. But that was 15 yrs ago, I don't get that now.

    Sent from my LS670 using Tapatalk
     
  9. Feb 4, 2011
    pathkiller

    pathkiller Member

    Lorton, VA
    Joined:
    Apr 17, 2005
    Messages:
    878
    Ethanol is an oxygenate, the same as the "winter mix" formulas. You can expect lower mpg when using it, but a 42% difference is extreme.

    There's no way you're running 4500rpm at 60mph with 3.73 gears and a 1:1 final drive with 27/28" tall tires. You shouldn't be taching more than 2800rpm with that setup. If your tach is reading 4500rpm it is definitely wrong.

    Seems to me the changes you have made have moved your mpg in the wrong direction. The stock setup was known to get high teens to low 20's from the factory. The modifications you have made result in 12mpg, so I would probably start by reconnecting the EGR and putting timing back to factory specs and seeing what you get.
     
  10. Feb 4, 2011
    DREDnot

    DREDnot Not new to JEEPS

    AZ
    Joined:
    Feb 7, 2010
    Messages:
    646
    I would save the money that you would spend on any intake and exhaust mods and get yourself some narrow,lightweight aluminum wheels and non-aggressive radial tires.
    You will notice a difference in acceleration immediately
     
  11. Feb 4, 2011
    0IIII0

    0IIII0 Nibblin' on sponge cake..

    Tempe, Arizona
    Joined:
    Sep 29, 2006
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    384
    Between 15-17 on the highway fully loaded; that's two people, camping gear and cooler. Also, that's with a T18, but my 4th gear is 1:1.
     
  12. Feb 4, 2011
    0IIII0

    0IIII0 Nibblin' on sponge cake..

    Tempe, Arizona
    Joined:
    Sep 29, 2006
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    My first reaction was to totally agree with changing the gear ratio to improve fuel economy, but after reading on-line for a while, it seems that the gear ratio change for fuel economy is nominal. I would think a Jeep is a Jeep and the best way to get good fuel economy is to make sure the engine is tuned and cooled properly. That's probaly about all you can do. :)
     
  13. Feb 5, 2011
    OleBlue

    OleBlue Sponsor

    Tennessee
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    Feb 14, 2010
    Messages:
    1,001
    I hope to get this when my CJ is back on the road. That's great mileage. My dad and I never knew the mileage since Blue was always a farm and hunting jeep. That's as good as the mileage my wife gets with her 09 JK Rubicon Unlimited!
    Posted via Mobile Device
     
  14. Feb 5, 2011
    sterlclan

    sterlclan Member 2022 Sponsor

    exploring the...
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    74 with a 232 i average 18 to 20 worse now with the hard top and locked hubs around 16 now...
     
  15. Feb 5, 2011
    CJ-ING-RJ

    CJ-ING-RJ Member

    Iowa
    Joined:
    Jul 29, 2010
    Messages:
    146
    I would be happy to get 12 to 15. Right now with a 258 I'm getting around 8 mpg. I know its far from tuned but hopefully soon it will be. On a side note my 08 JKU Rubi is only getting 13 in town and 16 on the highway.
    Posted via Mobile Device
     
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  16. Feb 8, 2011
    bobracing

    bobracing web wheeler

    Richland, WA
    Joined:
    Oct 28, 2007
    Messages:
    215
    Always try the HHO conversion, some say they get a nice boost in mpg.
    Never tried it so can't say yes or no if it works. There was someone on this board that did the conversion, very crude but said it bumped his mpg up significantly.

    http://www.hho-hydrogen-car.com/
     
  17. Feb 8, 2011
    joe28

    joe28 Member

    North Eastern Pa.
    Joined:
    Oct 21, 2009
    Messages:
    170
    Well I went last night to Firestone and got 4-31" tires.
    I had gotten a set for my sons 2 whl drive Jimmy Sonoma. He had told me they worked well in the snow, but a bit of a whine.
    The 225/75/15 we're 90"@ and these new tires are 97"@, so I picked up 7" per revolution.
    Between the 2" spring lift and these tires, (2" taller), good thing I have tall legs. I guess the next item is a nerf bar to step to get in.
    My wife had trouble getting in it with the spring lift, (she's "height impaired to begin with), (she doesn't ride in the jeep, she's afraid to get, "Shaken Mommy Symdrome")!;)
    I couldn't really feel a BIG difference driving home, but I THINK I had to wind the engine out a bit more between shifts, (I think it was me trying ot make it so).
    Today it snowed here, (3" of wet snow), so I couldn't really tell.
    I had my GPS and the speedo to actual MPH didn't change (well up to 35 mph was the fastest I could get in the snow).
    The ride seemed the same, bouncey wise.
    I'm gonna take the interstate on the way home for the final test.
    Yes, it does run 4000-4500 RPM 60-65, always seemed to.
    My '61 CJ5 with the 225 V-6 ran the same RPM to MPH, I don't think my flat heads ever turned 4 grand..............
    Next prehaps a port J.O.B. on the head and a header to let it "breath easier"
    Joe
    It's a jeep, your SUPPOSED tpo spend a ton of $$ on it!
     
  18. Feb 8, 2011
    73cj5

    73cj5 Member

    Maine
    Joined:
    Jan 15, 2004
    Messages:
    903
    This cant be right...(unless your in low range)
    Are you reading this off a tach? Is it on the 4 cyl setting? That would read 1.5X your actual rpm.
     
  19. Feb 8, 2011
    pathkiller

    pathkiller Member

    Lorton, VA
    Joined:
    Apr 17, 2005
    Messages:
    878
    It's impossible to be turning 4000-4500rpm with 3.73 gears at 60mph with a 1:1 final drive with 27" tires. You can use an RPM calculator to verify this: http://www.ringpinion.com/Calc_RPM.aspx It comes out at 2785rpm.

    With that setup the only combination that would yield 4000+ RPM would be if you were running 5.38 axle gears and 27" tires. If your tach is reading 4000 or more, it's wrong, simple as that, the math doesn't lie.

    With your new 30.5" tires and 3.73 gears the calculator says you will be turning 2465rpm at 60mph.
     
  20. Feb 8, 2011
    0IIII0

    0IIII0 Nibblin' on sponge cake..

    Tempe, Arizona
    Joined:
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    Interesting...I remember a 3-5mph difference when I upgraded to 31's.
     
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