1953-1960 Classic Car Engines Troubleshooting Guide: Pre-Ignition

The text for this Guide originally appeared in the 23rd edition of Motor's Repair Manual, published in 1960 and copyrighted by Motor Information Systems, and is used with their permission.

Things to Look For:

Pre-ignition means that the mixture is set on fire before the spark occurs, being ignited by a red hot spot in the combustion chamber such as an incandescent particle of carbon; a thin piece of protruding metal; an overheated spark plug, or a bright red hot exhaust valve. The result is reduction of power and overheating accompanied by pinging. The bright red hot exhaust valve may be due to a leak, to lack of tappet clearance, to valve sticking, or a weak or broken spring. Pre-ignition may not be noticed if not severe. Severe pre-ignition results in severe pinging. The most common cause of pre-ignition is a badly overheated engine.

When the engine won't stop when the ignition is shut off, the cause is often due to red hot carbon particles resting on heavy carbon deposit in a very hot engine.

The Complete Guide to Troubleshooting 1953-1960 Era American Classic Car Engines