L76 slowing idle then dies only when warm - NCRS Discussion Boards

L76 slowing idle then dies only when warm

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  • Bryan Pruett

    L76 slowing idle then dies only when warm

    I have a 65 L76 that runs slightly hot on the freeway and in city traffic. The car exhibits a slowing idle when hot to the point where it will die if I do not keep my heel on the gas at a stop light right after getting off the freeway. After getting off the freeway, the idle speed will start out at the normal 900, then slowly decline to the point where it dies. The Gauge will read 195 when this occurs. After running in city traffic for a few minutes, it appears the temperature will go down slightly (180 to 190) and allow the engine to idle normally.

    Anybody have any ideas why the idle will deteriorate like this? Solution?

    Here are the details on the car:
    Stock L76 with the exception of flat top pistons giving approx 9.8:1
    power nothing, no AC, 4 sp.
    rear end is stock 4:11
    Recently rebuilt, but ran hot (190-200) before rebuild. Was original bore, now 30 over.
    New De Witts radiator, correct disty with correct and operating vac advance.
    50/50 coolant mix.
    New stock type water pump.
    Original 5 blade fan and clutch.
    Timing correct.
    New hoses.
    Temp gauge reading verified with IR gun.

    Here is operating condition:

    Freeway driving in outside temps of between 60 and 80 degrees will result in the engine warming to 180. The temp will then slowly rise to 195 or so and hold.

    City driving will result in generally stable temperatures with the temp occaisionally rising to 195 at stop lights and then going back down to 180 when underway.
  • William O.
    Expired
    • April 30, 2001
    • 355

    #2
    Re: L76 slowing idle then dies only when warm

    It could be vapor lock... but my best guess is the fuel pump.

    Check the fuel filter.
    Check the fuel pump.

    Comment

    • Scott Butville

      #3
      Re: L76 slowing idle then dies only when warm

      I have seen this exact idle scenario on L76's that do not have the correct (or properly functioning) vacuum advance can.

      Comment

      • Duke W.
        Beyond Control Poster
        • January 1, 1993
        • 15643

        #4
        Re: L76 slowing idle then dies only when warm

        '63 L-76 exhibited idle instability from new because they had a 15.5" vacuum can, but only pulled 12" at idle. The fix is to install the '64-'65 L-76/84 vacuum can, which is locked full at 8"

        Original Delco's are stamped "236-16", and recent replacements "B28".

        The proper initial timing range is 10-14 and with full vacuum advance and a couple of degrees centrifugal since the cent. starts at about 700 should yield in the range 28-32 degrees total idle timing at 900.

        Verify that you have a correct specification vacuum can and also test it with a vacuum pump to be sure it doesn't leak.

        If the ignition map checks out then it's probably a carb. problem.

        Duke

        Comment

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