1970 LT-1 mpg

Discussion in 'Camaro Questions' started by Mrnmrssmith, Apr 9, 2020.

  1. mallard

    mallard Veteran Member

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    I guess it never occurred to me to test the MPGs in my 74z with the original L82 done up like an LT1 much like it never occurred to me to test my 2018 Acadia in the 1/4 mile. :bowtie::lush:
     
  2. G72Zed

    G72Zed Veteran Member

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    Very interesting post, but not surprised about the 1 mpg gain even though you made about an extra 50-75 HP give or take.

    It took me by surprise early on when building and testing stuff that more power did not actually mean worse gas mileage, and in many cases, went the other way. As I learned more and more things, by hard work, or by sheer luck, that as the parts became better matched and worked as a complete tuned package that fuel consumption went down accordingly.

    Working on heads/intake/carbs and dyno testing reveals some very key trends. It's nice when you hit your goals and the VE get over 100% and BSFC in the low .40"s all the while using less fuel to get there.
     
  3. badazz81z28

    badazz81z28 Veteran Member

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    Well actually more horsepower does burn more fuel just like you burn more calories by the harder you work. The reason today’s engines are so efficient is because computers can ratio fuel and air near perfection and adjust accordingly to the conditions. A carb can’t do that and a improperly tuned carb is going to waste fuel. Just putting a computer controlled fuel injection system on a SBC will improve its fuel consumption. I think the machining on the engine itself is negligible.
     
  4. 1978 Z/28

    1978 Z/28 Veteran Member Gold Member

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    I must disagree with badazz81z28 statement “I think the machining on the engine itself is negligible.” and “The reason today’s engines are so efficient is because computers can ratio fuel and air near perfection and adjust accordingly to the conditions” My poor under powered 1978 z/28 rated at 185hp@4000 was a slug compared to a 1985 z/28 with a 305 190hp@4800 with a 4 bbl and 45 less cu.in.
    In the late seventies auto markers built engines to emissions laws, engines with bad fuel economy and performance. The public feeling at the time was North America auto makers were trying to force governments to give up on emissions laws, but that did not happen. In the 80s auto makers started making hp again even as emissions laws got stricter and no efi.
    You have to have matching parts for an effective running engine, for either power, fuel economy or a combination of both.
    Watched an episode of engine masters with someone who can tune a carb, SBC Engine made 474hp with efi, 471 hp with 750 cfm carburetor and with 1050 cfm carburetor 480hp. So carburetor with same cfm of efi, made 6hp more.
    I do agree for the average person efi will make more power and use less fuel doing so and be more driveable than a carburettor.
     
  5. G72Zed

    G72Zed Veteran Member

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    I guess you didn't pick up on what I was getting at, but that's fine, everyone see's and grasp's things differently, or not. Some engine are, or can be made to be very efficient, be it FI or even carb'd, but that largely depends on ones experience and expertise and what they have to work with.

    I know an engines mechanical's efficiency, or better yet to focus on minimizing the losses (frictional,alignment,parasitic and phasing) has much to do with machining. So I will respectfully disagree with your last sentence.
     
  6. badazz81z28

    badazz81z28 Veteran Member

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    The conversation is going into different directions...comparing the engines ability to make power versus being fuel efficient...I'm focusing on the engine being efficient (in a certain sense). There is a lot of margin of error in a carb engine that can cause it to be a fuel burning pig. Engines are vacuum pumps...air and fuel goes in, its burned and expelled. How much of that fuel is getting burned? How efficient is the air traveling through the induction system and exhaust being scavenged (to get the cylinder full)? Modern engines make more power due to many factors, things like variable timing, electronic fuel injection, cylinder head design, reduced parasitic loss etc. Old smog era engine didn't have the best of design intakes and heads for maximum power. They were designed to be emission compliant and that killed power. However a perfectly tuned engine will give you better fuel economy than one that isn't (ie a improperly tuned carb versus a EFI system). I'm not comparing engine designs, of course a better design will yield more power and better efficiency, but the below poor efficiency of old engines has a lot to do with tuning. Yall make it seem the the precision of the machining of the cylinder bore was the game changer, and I don't think so.
     
  7. 1978 Z/28

    1978 Z/28 Veteran Member Gold Member

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    This is not what I said. Yall make it seem the the precision of the machining of the cylinder bore was the game changer, and I don't think so.[/QUOTE]
    If an efi had mismatched parts it too would be fuel burning pig. An efficient engine is the sum of parts and tuning being a carburetor or efi. If an engine has a bad plug, with or without efi the engine will not be efficient.
    I also said a person with the ability to tune a carburetor, can tune the engine to make the same or more power or be as efficient as an efi engine of the same design and parts.
    If you compare modern engines to early engines, then the modern engine is more efficient, but not just because of efi, but all the reasons you listed
    On an early sbc a well tuned engine with a carburetor will work just as good as efi
    tuning is the issue
     
    Last edited: Apr 14, 2020
  8. DanSaco

    DanSaco Member

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    I can’t believe this subject has never come up before, I mean has never occurred to me I drove my 70 for 7 years without ever once considering checking the fuel mileage. Stock 95 350 converted to carb, th350 3:08 gear. After I button up a few things it will be back on the road with a 72 LT-1 and a 2600 stall converter. Would have assumed that the addition of about 130hp would sink the mpg, but the question of energy efficiency does make one wonder.
    Future plans are to change to a 3:73 or 4:10, and a 4 speed if I can find one. I’d love a 700r4 just for their drivability.
     
  9. 76z28

    76z28 Veteran Member

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    I know people are busting your balls, but I go to a carshow on the coast once a year and stop in the same place for fuel each year.
    When I had the small block and 3.73, th400 3500 stall 700 holley: 10mpg--speed was 65mph
    Next year I had the big block and 3.73, th400 3500 stall 850 demon: 7mpg--speed was 65mph
    Last drive out I had the big block, 3.73s, th400 3500 stall and Proflo 3: 11mpg--speed was 65mph
    Next time(Hopefully soon but looking doubtful) big block, t56 magnum, 3.73s and proflo 3: 17(hopeful) 65mph.
     
  10. Farm Boy

    Farm Boy New Member

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    In early 1973 I bought a Cortez Silver 1970 Z28 with a Muncie M21 and a 4.10 rear end. The car was completely stock with 33,000 miles. I was getting 10 MPG. I'm sure I could have gotten better mileage with a lighter right foot, but I was 16 years old and it was a blast to red line the LT-1. The October 1973 Arab oil embargo caused gas prices to double. I could no longer afford the fuel and insurance so I sold it.
     

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