mpg on a '75 Clamshell-What should I expect?

Discussion in 'Fuel Economy & Emissions' started by Glide-Aways, Sep 28, 2008.

  1. Dyna

    Dyna Well-Known Member

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    :) -- I think I wrote "isn't much you can do to get things better than that. Unless we start to modify." Ignition curves is one of the obvious modifications you will do to get better MPG....

    Cheers Dyna

    BTW: 12 MPG is pretty darn good ....

    Here is one that is worse:
    2009 BMW M5 (thats a sedan and a V10) 11MPG and that is the official figures we all know you never get in reality ;)
     
    Last edited: Nov 6, 2008
  2. Stormin' Norman

    Stormin' Norman Well-Known Member

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    I'll read your posts much slower next time. :)
     
  3. Dyna

    Dyna Well-Known Member

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    LOL we all rush :banana:

    Dyna
     
  4. Taranau

    Taranau Well-Known Member

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    mpg's

    My family had a 74 Ford LTD Brougham,with a Ford 400,for a little while.And,while we used to joke that it got gallons per mile instead of miles per gallon,it's owner's manual was saying it was supposed to be getting 10 city and 14 highway.It was a 4800 pound car.If your wagon weighs too much more than that,then your mpg's will be a bit lower.8 and 12 was supposed to be the lowest,according to Federal standards.9 and 13 and 10 and 14 were average numbers for vehicles with engines in the 400 area...Put a person in every avaiable seat,however,and you could drop down to 5 or 6 mpg.
     
    Last edited: Nov 29, 2008
  5. The Stickman

    The Stickman Well-Known Member

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    If you want to up your mileage you can either swap out your rear gears or put an overdrive transmission in it. I have a 2.73 rear witha 200R4 transmission with overdrive and I have gotten 20-25 on the highway with the 307. Now I haven't had my 350 running enough to do a mileage test but I think there is the potential for it to go up.
     
  6. Glide-Aways

    Glide-Aways Well-Known Member

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    My MPG

    Hey Everyone,

    Thanks everybody for your advice and insights. :clap: I tuned up my engine and have noticed a modest improvement. More importantly, your insights have helped align (pun intended) my expectations, so once again thank you!
     
  7. ross

    ross Well-Known Member

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    I had a tired old Suburban of similar vintage that could at least equal those numbers.
    Seems you should do better.
    I'd have a good look at the distributor, carb and zillion vacuum devices on that car to be sure they are functioning correctly and unmolested.
    Emission controls were pretty crude in '75, lots of driveability problems were corrected in the field by simply richening the mixture or farting around with ignition timing.
     
  8. Glide-Aways

    Glide-Aways Well-Known Member

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    Hi Everyone, and HAPPY NEW YEAR! :party:

    I've not been on this forum in ages...am on the tail end of my busiest season at work. Nice to catch up on everyone's latest happenings. :)

    Just wanted to drop a note here to thank everybody for their advice and input regarding my mpg question. I gave my wagon a tune-up and noticed a slight improvement. I've also noticed I tend to get better mpg during the first half tank compared to the last half. Any ideas why this may be, or am I just imagining this..?

    On to read more posts...:2_thumbs_up_-_anima
     
  9. Stormin' Norman

    Stormin' Norman Well-Known Member

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    The float is soggy. Same thing with mine. The float get all gummed up over the years and doesn't show an accurate reading on the gauge. No big deal unless you want to replace it. A new tank sender runs into a c-note or more. I think you can clean it, but you'd have to get some of the right gasket material first. If it's cork, you'll have to replace it. Brass can be cleaned.
     
  10. Taranau

    Taranau Well-Known Member

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    those fuel meter needles

    It's been a "news report",every now and again,here in L.A:confused:...Gas gauges have a tendency to more accurately measure a full tank than one that's getting empty:).The last quarter tank is the least accurately measured:(.The last quarter tank is also the most likely to have "gastank gunk" floating around in it:49:,which'll get caught up in your fuel filter(hopefully not clogging it):(.It is suggested,by the news reporters,that you fill up when you have a quarter tank left,not less than that,for that reason:).It works that way with the worktrucks I use(US Mailtrucks):(Some will say they have an eighth of a tank left and be running on fumes:49:Others use a half a tank going thirty/thirty-five miles of city driving.:slap:
     
  11. occupant

    occupant Occupantius

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    I don't think a 200-4R would be good for a heavy car like that with a 400. It's a Chevy small-block, a 700-R4 would be perfect. Shouldn't require too many modifications other than something to engage lockup. Bauman and TCI make controllers for that.
     
  12. turbobill

    turbobill New Member

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    Three things will help with your car. An overdrive transmission with locking torque converter, a true dual exhaust and some super tuning. As most of your driving is city, a low stall speed torque converter will be best as it won't be locked up very much.

    If you want to dive a little deeper, a raise in compression ratio will help a little, but probably not be worth the work and expense.
     
  13. Tarjei

    Tarjei New Member

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    MPG and a little moore

    Hello
    I have read all this topic about MPG with interest. I use 73 Buick Estate wagon with 455 as a daily user, and for some months ago i start " increase mpg " prosject. The car is unrestored and the speedo says about 110 K
    In the beginning the car use 6 - 8 mpg, and here in Norway the fuel cost average 9 $ pr gallon, so i have to do something.
    First i change spark plug, wire , points etc, with little difference. Later i rebuilt the rochester with new gaskets, who help a little, but not much.
    The big difference came when i give the engine a new timing chain and camshaft with lifters
    I dont tell that the car have bad performance before this operation.
    After the last operatioan the car run like new, and the mpg is now much lower.
    average 10 -12 mpg, and with this big car, i think i much expect this level. Perhaps i change the tranny to a 200 R4, and lower the mpg the last 5 -10 %. ( the next step must be other engine, but i want to use this 455..... )
    This car is konverted to LPG, but i want to optimize the original performance before i began to use gas. I have my own buiseness ( www.drakechemicals.com ) ( www.stripall.no ) and plan to use this car to promotion for my products . At last there are picture of 2 happy girl, who have been with their father on x -mas shopping..........
     

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    Last edited: Dec 26, 2010
  14. MikeT1961

    MikeT1961 Well-Known Member

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    There are several things to be done:

    1) Start with an efficient high-torque intake. The Edelbrock Perfromer works really well. Put on the Edelbrock Q-jet 4bbl split bore carb, and tune it properly. Adjust the idle mixture until the idle is at its highest. When you get the carb, talk to the techs at Edelbrock. They will well you the best jetting to install for how you use the car.

    2) Install a GOOD set of ceramic coated long tube headers with a 3 inch collector. Use DUAL cats! Have the shop install an X cross over, and use FlowMaster Delta Flow mufflers.

    3) If you don't want to change the transmission, install a GearVendors overdrive. Otherwise, use a heavy duty mechanical overdrive from a laate 80s 1 ton small block truck.

    3) Choose the right tires. If I remember right, the stock size is somewhere around H or J/78R15. Use a 235/70R15, and something like the Pirelli P3000 in a 100H. The H speed rating means a stronger carcass.

    4) If you ever have to change the cam, talk to Comp Cams about the highest torque grind they make.

    5) Advance the timing until just before ping sets in.

    6) Done right, with every mileage making trick, you should be able to get into the 30s on the highway. My brother had an 86 Colony Park, 351W and tow package, that did about 34 mpg (U.S. gallon). That was when the engine and tranny had almost 500,000 miles on them.

    Good luck. The complete upgrade will run about $5,000.00. It can, of course, be done in stages as things need doing.
     
  15. 350x

    350x 'Echinsu Ocha'

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