Article 1987 - Engine Detonation and/or Pre-Ignition

TSB #126 - November 7, 1969
(All Engines)

Because of damage that will result from prolong periods of detonation or pre-ignition it is important the cause be located and corrected immediately. A list of items that will influence the tendency to detonate appears below.

    1. Substandard (low octane) fuel being used.
    2. Engine initial timing adjustment incorrect.
    3. Distributor calibration incorrect.
    4. Lean fuel mixture due to incorrect carburetor, carburetor components, low float adjustment, and/or air leaks into the induction system.
    5. Fuel pump pressure and/or flow insufficient.
    6. Spark plugs that run too hot for the given application, or plugs with cracked and/or broken ceramic cores.
    7. Carbon deposits and/or sharp edges in the combustion chamber than burn and remain incandescent.
    8. Valves operating at higher than normal temperatures because of an improper seal with the valve seat caused by dirt or foreign material, bent valve, or improper tappet operating clearance.
    9. Engine operating temperatures too high due to:
      a. Low coolant level.
      b. Defective thermostat.
      c. Defective radiator pressure cap.
      d. Cooling system aeration.
      e. Drive belt tension too low.