HEI Ignition Coil

Written by: Mike Ervin

Checking and replacing the ignition coil.

  • Disconnect the negative battery cable.
  • Remove the distributor cap.
  • Position the cap upside down so you can see the male spade-type terminals inside the hood protruding from the coil cap.  Connect an ohmmeter to the outer two terminals.  The ohmmeter should indicate very near zero resistance.  If it doesn't, replace the coil.
  • Connect the ohmmeter between the TACH terminal and the center terminal of the distributor cap (inside the cap where the rotor touches) and note the reading on the ohmmeter.  Move the ohmmeter lead to the ground terminal (center terminal on the inside row) and leave the other lead on the center terminal inside the distributor cap.  Be sure to use the High scale.  If both ohmmeter readings indicate infinite resistance, the coil is faulty.


  • Remove the coil cover screws and lift off the cover.
  • Carefully push the coil spade terminals through the top of the hood with a small screwdriver.
  • Remove the ignition coil mounting screws and detach the coil, with the wires, from the cap.
  • Remove the arc seal (rubber pad under the coil).
  • Clean the coil housing and the rest of the cap with a soft cloth and check the cap for defects.  Replace if necessary.
  • Install the new coil and tighten the mounting screws securely.
  • Position the terminals in the correct slots, then install the coil cover on the cap and tighten the screws.
  • Install the distributor cap.
  • Reconnect the negative battery cable.