Topic: 79 ta getting horrible gas mileage need insight

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  • anti_chrysler’s Profile Photo
    Apr 14, 2011 at 10:53 pm
    my friend has a 79 ta with a buick 455/ 400 trans.
    stock rear end. 255/50/15 tires.
    motor besides being a swap is all stock.
    the carb is an edelbrock 600 4bbl.
    the trans works beautifully.
    he is only gettin 5mpg and he drives like sissy.
    any insight as to possible problems would be appreciated.
    also he is considering using a 454 tbi system on it. any pros and cons of this would be cool too


  • lastofthebest’s Profile Photo
    May 4, 2011 at 9:23 am
    hello it sounds like u may have a gass leak there is a return line ont the passenger side of the gass tank that is a very common rott spot. and it also only leaks when you are driveing the car lol so you way want to check that spot maybe that will help good luck


  • rickyb1961’s Profile Photo
    • Join Date: Nov 30, 2008 at 8:28 am
    • Total posts: 17
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    May 6, 2011 at 1:30 am
    My first question is just how healthy is the 455? Is there a vacuum leak somewhere? How well was the exhaust routed? What year is the engine? Is the distributor advance working correctly?

    As for suggestions, after making sure the fuel system is not leaking, the next step is to adjust the carb. Number one is are the correct metering rods for the application installed? Once that is done, adjust the idle mixture. Most people set the carbs too rich. The idle should be dead smooth, and on a knife edge. About 1/16th of a turn either direction should degrade the idle. There is a knack to it. Next, check the timing. If the engine is older, check for play in the timing chain. If freshly built, the cam could be off by one tooth. That's all it takes. Set up right, it should be doing about 20 -25 mpg on the highway when driven gently, but not too gently. Also, the stock rear end may be too high numerically for the torque curve. the Buick 455 is a torque monster. You need the revs down in the mid teens for good mileage. Overdrive may be the way to go.

    As for the fuel injection, if the throttle body will mate to the Buick intake, it should work. You might also try the F.A.S.T. throttle body bolt on. It is self tuning, and then you can optimize from there. You might also consider the Edelbrock Performer (BUT NOT RPM) intake. It is designed for torque.

    I would bet that is everything was done right and working properly, you could get the wee beastie matching a Honda Civic for mileage. Good luck.



  • 1blk1’s Profile Photo
    May 18, 2011 at 1:48 am
    have carb checked...could need rebuild


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