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Technical Fuel mileage

Discussion in 'The Hokey Ass Message Board' started by Racer29, May 25, 2017.

  1. As I looked down to the dash of the Peterbilt 579 that I drive for work and saw the fuel economy gauge it got me to thinking about what most hot rodders get for fuel mileage. Me personally I'm not too concerned with the mileage that my '29 sedan with 472 Caddy engine gets. Although it will get 14 mpg cruising at 65. Bump that up to 75 and it drops to 10-11 mpg. Now the '51 Hudson, stock as a clock 262 flat 6 ,is the fuel economy car. It will get about 20-22 mpg out on the highway and 17-18 around town. Now I know most of us don't build them with fuel economy in mind but I don't mind the bonus of not breaking the bank for fuel.

    Sent from my A520L using The H.A.M.B. mobile app

    Attached Files:

    Last edited: May 25, 2017
    51hornetdude and chryslerfan55 like this.
  2. I dump about $45 worth of 93 octane in my '59 Ford a week... add another $20 if I toss in an octane booster. I'm tracking my MPG this week, the last time I did I was getting around 10 MPG. I've had my foot out of it a bit and drove normal for a few days, be happy if it hit 12.
    chryslerfan55 likes this.
  3. Jalopy Joker
    Joined: Sep 3, 2006
    Posts: 27,712

    Jalopy Joker

    depends if you do long distance or stay close to home, or 1/4 mile at a time. with some planning & engineering can get some good mileage out of a pretty wild ride.
  4. cb186
    Joined: Jul 5, 2013
    Posts: 263


    52 Ford with a 52 Merc flathead, stock except for Iffy 400 heads, overdrive, 3.90 gears. 18-19mpg mostly highway running ~65. Motor needs to come apart because one cylinder is real low on compression. Probably get better economy if it was sealed better.

  5. I'm guessing the gears in your 472 powered sedan must be kinda low. I had one in its factory location- 68 sedan deville- that got at least as good of mileage. I think it had 2.73 gears but assume it would roll across the scale at 2.5 to 3 times as heavy as a 29? Best mileage I understand is around the engines peak torque which is pretty low in that one.

    Sent from my iPhone using The H.A.M.B. mobile app
  6. Petejoe
    Joined: Nov 27, 2002
    Posts: 11,150

    from Zoar, Ohio

    8ba Flathead 37 coupe running two 94's and highway gears. 16-18 on four lane.
    My 34 truck 59a flathead with dual strombergs lower gearing. Running 10mpg at a max of 60-65 mpg.

  7. Truck64
    Joined: Oct 18, 2015
    Posts: 5,227

    from Ioway

    Checking fuel mileage is probably the easiest method to determine if a stock or stockish engine is properly tuned, even if economy isn't important. If fuel mileage isn't what the engine and drivetrain is capable of, you ain't done tuning.

    Mostly, best performance always equals best mileage, at least if you can keep your foot out of it. When the ignition timing curve isn't optimized, carburetor air fuel mixture, jetting, power valve etc out of tune, weak spark, then efficiency will suffer. Slightly rich air/fuel mixture is better than going too lean, but it does waste $$, fouls plugs, and if extreme washes out rings and dilutes engine oil.
    jp52 and 120mm like this.
  8. anthony myrick
    Joined: Sep 4, 2009
    Posts: 8,915

    anthony myrick

    6500 pound bus with a 350/th400 rochester 4v and 410 gears gets around 10-12 on the hwy
    good guys bus 2 (1).jpg
    hipster and 1964countrysedan like this.
  9. <<< 18-19 mpg @ 70-75 mph. Used to get 20-22 mpg with a 250*-260* XE Comp. ;)
    Tim_with_a_T likes this.
  10. 3.23 rear gears. At 70 mph its turning 2600 rpm. Holley spreadbore 650 Double pumper carb. The car runs excellent except maybe a hair fat on fuel. I think if I had the 2.73 rear it would drastically improve.

    Our old '47 Hudson with FE390 got 9 mpg when we first bought it. 3.08 rear. After a good tune and fixing some ignition issues it would average 16.

    Sent from my A520L using The H.A.M.B. mobile app
  11. squirrel
    Joined: Sep 23, 2004
    Posts: 50,253


  12. hotrodyankee
    Joined: Jun 27, 2016
    Posts: 304


    283 power pac, dual quads, carter afb's, 400cfm. with the 3.73 gears, 31"rear tires at 60mph and at 2300rpm I get 16.4 mpg. Good enough for me.
  13. tfeverfred
    Joined: Nov 11, 2006
    Posts: 15,792

    Member Emeritus

    Never cared. Hondas are good on gas, though.
  14. Blue Moon Garage
    Joined: Mar 1, 2009
    Posts: 300

    Blue Moon Garage

    21+ mpg @ 75mph on I-25. 351 Ford crate motor, AOD, 3.70 rear. Repeatable over and over. 14-15mpg in town. Ft. Craig rest stop 3-3-17.JPG
    Legends47 likes this.
  15. TagMan
    Joined: Dec 12, 2002
    Posts: 6,181


    My '37 Chevy coupe has a 1961 235 engine, 3.73 rear axle and a B-W overdrive in the torque tube. On a trip to Rapid City, S.D. and a bit into Wyoming & back, a round trip of about 3400 miles, mostly on I-90 at 70+mph, I averaged 22.8 mpg.
    Around town, without the OD, I get around 17-18 mpg.
  16. stimpy
    Joined: Apr 16, 2006
    Posts: 3,547


    don't care , as the D/D's and play toys do not make me money but get me to work or out , on the big truck yes milage is a important thing as it cuts into the bottom line of my profits .
  17. gimpyshotrods
    Joined: May 20, 2009
    Posts: 19,130


    My Falcon gets 32mpg with the current engine, but is altitude sensitive.

    The new engine is going in soon. It has EFI and full digital engine management. That will automatically compensate for altitude.

    It is way cooler than a Honda.

    Poor mileage is often a combination of improperly matched parts and poor tuning , rather than anything else. I weld O2 sensor bungs into everything I tune. I have doubled the MPG on several engines that I have tuned.

    There are only four places that the fuel can go: power, heat, leaks, or out the exhaust.

    Wasting fuel due to improperly matched parts and/or poor tuning is not a badge of honor. It is just throwing away money.
    hipster, Bomb, Tim_with_a_T and 7 others like this.
  18. plym_46
    Joined: Sep 8, 2005
    Posts: 4,018

    from central NY

    17/18 around town, 20/22 on trips. 230 flathead six, dual singles, 4.11 rear end.
    On the highway I run about 3200 rpm (63 mph on the GPS). Will run to 70 but stock brakes feel better at slower cruise.
  19. Fordors
    Joined: Sep 22, 2016
    Posts: 3,951


    In '90 I think it was I drove my '32 coupe with a 6-71 blown/two 600 Holley 350 4 spd, to OKC with two friends. One guy had a '31 Chevy coupe with an LT1 that he had put a L79 cam in and he changed the 780 Holley to a 600. The other guy had a '31 Tudor with a TR-1 tunnel ram with two 600 Holleys on a 350. The surprise was on them- they thought I'd always be holding them up stopping for gas but all three of us averaged 17-17.5 MPG on the road running 70 MPH.
    3.36 gears, 31" tall tires and a well tuned combination gave the best of both worlds.
    Tim_with_a_T and Kan Kustom like this.
  20. Gene Boul
    Joined: Feb 9, 2006
    Posts: 805

    Gene Boul

    My 38 gets about 10 MPG. It has two Stromberg 48's, 4:40 gears, 950 rear tires a melling cam, Sharp heads, Fenton headers and Johnson adjustable lifters. I have a 39 trans with Zepher gears. I have never had the interest in pushing the cluster out on the I don't rod it!
    IMG_0787 5.jpg
    hendelec likes this.
  21. squirrel
    Joined: Sep 23, 2004
    Posts: 50,253


    ....but I'm hoping to get 20 with my new Corvair.


    (still putting stuff back on the motor that the PO removed)

  22. seb fontana
    Joined: Sep 1, 2005
    Posts: 7,209

    seb fontana
    from ct

    My 47 car gets around 32 mph, all around... Crosley 032.jpg
  23. seb fontana
    Joined: Sep 1, 2005
    Posts: 7,209

    seb fontana
    from ct

    However my shoebox gets 13.7 around town and two laners up to about 60 mph in 5th, on four laners at 80 mph in 6th and its 14.7..Can just make about four hours then time to fill up but I have to stop to pee at 2 hours!!
    Jeepnjay likes this.
  24. belair
    Joined: Jul 10, 2006
    Posts: 8,803


    My truck gets 18. 10 on the hiway and 8 in town.
  25. ...20+ with a 250 Chevy six, the real small block Chevy..
    gmc build 008.jpg
  26. threewindow
    Joined: Nov 26, 2012
    Posts: 80


    I drove my 51 merc back from the stray cat 500 at 70 to 75 miles an hour with the air on all the way. It's got a 350 350 with 273 gears. I got 22.8 miles per gallon. Got a quadrojet that I've had apart several times. Can't beat them for gas mileage. Went 205 miles on 9 gallon of gas.
  27. ROADSTER1927
    Joined: Feb 14, 2009
    Posts: 2,936


    My Roadster has 6/ Stromberg 97's 49 olds engine with 10.5 comp flowed 55 heads and an old Isky full revmaster cam. It has 31.5" rear tires and I usually run a 4/11 gear in the quickchange , over the whole year I get 12.5 mpg. Some days it is about 4 and others 18 , just the fun factor varies! Gary

    Attached Files:

    belair likes this.
  28. Tman
    Joined: Mar 2, 2001
    Posts: 35,154


    My old 54 Chevy sedan got 18-20 all day long with the 350/400 combo and 2.73 gears
  29. My Model A w/322 Buick (avatar) th350 tranny and a 3.08 rear got 18.4 mpg the last time I check, happy with that.
  30. '47 chevy coupe, 216 babbitt 6-cyl, t5, 3.08 rear, 28" tire, two one barrel Rochester carbs, electronic distributor, 22 MPG highway, no idea what it gets in town, but it is smiles per miles not miles per gallon.
    belair and bobss396 like this.

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