What are the published MPG specs for 1973 350 and 455 in the full size cars?

Discussion in 'A boatload of fun' started by garybuick, Dec 1, 2016.

  1. garybuick

    garybuick Time Traveler

    Somewhere there must be sales literature from the period that tells the mpgs. Anybody know?
     
  2. 66electrafied

    66electrafied Just tossing in my nickel's worth

    They really didn't harp up much on the fuel economy for 73; it fact it wasn't even a consideration, by 75-76 it was far more important. 1973 was the last year of cheap gas before the energy crisis. Most published figures published after that until about 1979 were bogus anyway. I think the EPA got teeth in 77 if I remember right. I just went through my copies of the 74 and the 75 dealer brochures and there wasn't one mention of fuel economy in the 1974 book, in fact they recommend the 350 V-8 for the Apollo, but in the 75 it had changed; they were really playing up the "new" 3.8 litre V-6, which they had just re-liberated from AMC. It was considered "fuel-saving', but there were no numbers to back it. All the small cars had a more "Euro-feel" and that was definitely the focus, whereas in 1974 it was still power and luxury.
     
  3. garybuick

    garybuick Time Traveler

    I wonder if my 73 350 is getting the optimum mileage or not. I dont even know whats healthy. and what about 455, what mpg can one hope for in a 73 LeSabre?
     
  4. 66electrafied

    66electrafied Just tossing in my nickel's worth

    My experience with either engine in that size of car is about 13-18 mpg highway, depending on axle, and in town it's like flushing a toilet, between 5 and 8 mpg, depending on how much one lays into it off the line. There's a reason not many of these cars survived; they were pigs. Most cars from the early-mid seventies were because of all the emissions crap and the down-tuning. By the time the 76 LeSabre was rolled out with the V-6 that car was so slow a modern 4 cylinder would be able to dust it, and of course, the fuel economy required to get 2 tons into motion was pathetic. The car didn't have the power to get out of it's own way, but , surprisingly enough, it wasn't all that much worse than the 350 2bbl. And yes, this was the forerunner to the wonderful 3.8 that powered Buick into the 21st Century.

    I've always wanted to stuff a 1970-71 455 Stage 1 into a 74 LeSabre and see what difference it would make using a more efficient high-compression engine that was unencumbered with emissions and de-tuning.
     
  5. garybuick

    garybuick Time Traveler

    do you know of any flowmeter that can go between the pump and the carb that measures fuel flow volume. This way I can get an absolutely accurate measure of how many gallons for a given amount of miles on the odometer. Does such a thing exist?

    edit: What about this? http://www.ebay.com/itm/Pro-K24-Tur...-For-Chemicals-Water-Color-blue-/122171979728

    [​IMG]

    or this one
    s-l500.jpg
    heres the link. http://www.ebay.com/itm/4-digital-P...789749?hash=item4af55860b5:g:dcIAAOSwcBhWZ8Wn
    Im tempted to get this!
     
  6. Brad Conley

    Brad Conley RIP Staff Member

    Ummm, how about just doing it the old fashioned way, with math? Miles driven divided by gallons used equals miles per gallon. Do it over the course of several tanks and you'll get a pretty good idea of where your are MPG wise.
     
  7. sean Buick 76

    sean Buick 76 Buick Nut

    I have had a lot of 73-76 Buick 350 powered vehicles and averaged between 12-18 mpg with them but as stated above in the city they will drink fuel... I actually got better fuel mileage with the 2 barrel carb as I was not hammering it as much as the 4 barrel. But I was getting places quicker with the 4 barrel for sure.

    I did an experiment with a 33,000 mile century 350-4barrel and cut off the exhaust ( so single 2.5") and re curved the ignition with a hei dist, put a new old stock q jet for a 73 Buick on and new plugs, wires, cap and rotor. Before these mods it barely got to 60 mph and after it ran much stronger. No other mods to the engine at all.

    https://m.youtube.com/watch?v=Qy1cOuE4x4Q

    https://m.youtube.com/watch?v=GljRr5PauLI

    https://m.youtube.com/watch?v=nbiqdPVLpnE

    Once I knew it ran well with less exhaust restriction I added headers and dual 2.5" with magnaflow and it still sounded good but more legal... Had to part that car out due to rust under the vinyl roof but still have the engine here in my garage... Tore it down and its 100 percent new looking in all ways no wear shown on the bearings or anything even after my abuse... I got it at 33,000 miles and put 2000 HaRD miles on it, but never any issues. Did a road trip and got 21 U.S. Mpg over 900 miles.
     
  8. garybuick

    garybuick Time Traveler

    I will use math. But with the flow meter I will have an accurate value for gallons used instead of guessing when the tank is as full as it was the last time I got gas. Besides that, if you do it that way you only get an average mpg of different kinds of driving. It would be great to have a meter tell me at the end of a short trip exactly how many gallons I used. Then i could divide the exact miles by the exact gallons.

    Even just an inline sending unit that would connect to a laptop in the car. That would be cool.
     
  9. garybuick

    garybuick Time Traveler

    21mpg? Thats excellent! What trans and rear end?

    here is the best one. It is pricey but designed to use on engines on a test stand.
    https://www.instrumart.com/products/10035/flocat-sf45-a-turbine-flow-sensor

    another way would be to find a really sensitive scale to drive the car onto before and after to calcuate the fuel used by weight. I think there are pressure pads you can buy foreach wheel. I have seen guys use them for tuning weight distribution for handling and racing.
     
  10. 66electrafied

    66electrafied Just tossing in my nickel's worth

    Yeah, I wouldn't fool around with anything that could potentially leak, rupture, percolate, or melt; there's a lot of heat on the manifold, not to mention, you'd be disrupting the flow characteristics by potentially creating a well, in effect dropping the pressure and then preventing effective vaporization of the fuel. The fuel system is best left intact and alone, the math is much easier and for the most part fairly accurate. At most the difference between fills would be a a quart or two; - nothing in other words.

    Sean's experiments in improvements work; - open up the engine and allow it to breathe and open up the plug gaps and load in high power spark, the thing will be more efficient. That said, there is one given, that is the amount of fuel in the amount of air that is required by that engine to run will not change; the mixture will either be too lean and stop, or going the other way, too rich. This is the point where physics takes over and will not permit anything else to happen. The 100 mile per gallon carbs are a myth; the engine will burn what it needs, otherwise it will stop, simple as that.

    Those engines from the early to mid seventies were choked-out low compression dogs; they needed whatever they could get just to stay alive. There aren't many earth shattering modifications you can do to them, 20 mpg is going to be about the best you'll ever do with one.

    If fuel economy is a concern, stick with the recent crop of modern Buicks; that 3.8 turned out to be a real sweetheart considering Buick gave it away to AMC in the early 70s, only to buy it back once they discovered that the 250 was a technological dead-end.
     

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