1961 Corvette - 283 cui / 270 Hp - NCRS Discussion Boards

1961 Corvette - 283 cui / 270 Hp

Collapse
X
 
  • Time
  • Show
Clear All
new posts
  • John W.
    Infrequent User
    • April 1, 2002
    • 5

    1961 Corvette - 283 cui / 270 Hp

    Does anyone know why the ballast resistor with a dual point distributer gets hot and if this is normal or not?
  • Jimmy G.
    Very Frequent User
    • November 1, 1979
    • 976

    #2
    Re: 1961 Corvette - 283 cui / 270 Hp

    Fairly normal That is why they occasionally burn out and that is why they are surrounded by ceramic material.
    Founder - Carolinas Chapter NCRS

    Comment

    • Frank D.
      Expired
      • December 27, 2007
      • 2703

      #3
      Re: 1961 Corvette - 283 cui / 270 Hp

      I've had a stock 270hp '61 for 10 years...a hot ballast resistor is perfectly normal.
      And, that's pretty much the case for any classic car of '60s and earlier vintage.

      Comment

      • David R.
        Very Frequent User
        • June 29, 2014
        • 183

        #4
        Re: 1961 Corvette - 283 cui / 270 Hp

        Generally speaking, electrical resistance = heat. Sounds like normal operation to me.

        Comment

        • Duke W.
          Beyond Control Poster
          • January 1, 1993
          • 15671

          #5
          Re: 1961 Corvette - 283 cui / 270 Hp

          Power dissipated in an electrical circuit is I**2*R... that's current squared times resistance.

          All C1s use the 0.3 ohm ballast, and primary coil resistance is about 1.0 ohm, so total circuit resistance is about 1.3 ohm.

          I = V/R, so at 14 volts I = 10.7 amps, but the circuit is intermittent and the average is about 5 amps, so total power dissipated by the ballast is about 5**2 (0.3) = 7.5 Watts and about 25 Watts in the coil. With appropriate unit conversions, Watts (power, which is energy per unit time) can also be expressed as BTU per unit time, which is the rate of heat generation.

          7.5 Watts is a lot of power dissipation for the small mass of the wire, so it gets hot.

          You can run the calculation for the 1.8 ohm ballast.

          The ballast wire is a special alloy that has increasing resistance with increasing temperature, so it acts as a current limiter to prevent excess current that can burn the points and excess coil temperature that can damage the coil.

          Look up posts by the late Dale Pearman from the early days of the TDB, and you will find that he refers to the ballast as an "analog computer", which is a correct representation albeit, it's about as crude an analog computer as can be imagined.

          Duke
          Last edited by Duke W.; July 29, 2016, 10:30 AM.

          Comment

          • John W.
            Infrequent User
            • April 1, 2002
            • 5

            #6
            Re: 1961 Corvette - 283 cui / 270 Hp

            great, thanks for your comments!

            Comment

            Working...
            Searching...Please wait.
            An unexpected error was returned: 'Your submission could not be processed because you have logged in since the previous page was loaded.

            Please push the back button and reload the previous window.'
            An unexpected error was returned: 'Your submission could not be processed because the token has expired.

            Please push the back button and reload the previous window.'
            An internal error has occurred and the module cannot be displayed.
            There are no results that meet this criteria.
            Search Result for "|||"