1953-1960 Classic Car Engines Troubleshooting Guide: Spark Knock, Ping, Detonation

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:

All three expressions mean the same thing. It is a sharp metallic knock caused by vibration of the cylinder head and block. The vibration is due to split-second high-pressure waves resulting from almost instantaneous abnormal combustion instead of the slower normal combustion.

The ping may be mild or loud. A mild ping does no harm but a severe ping will reduce power. A very severe ping may shatter spark plugs, break valves or crack pistons. Pinging is most likely to occur on open throttle at low or moderate engine speed. Pinging is encouraged by:

1. Overheated engine.
2. Low octane fuel.
3. Too high compression.
4. Spark advanced too far.
5. Hot mixture due to hot engine or hot weather.
6. Heavy carbon deposit which increases the compression pressure. Tendency to ping increases with mixture temperature including high atmospheric temperature; intake manifold heater valve "on" when engine is warm; hot cooling water; hot interior engine surfaces due to sluggish water circulation or water jackets clogged with rust or dirt especially around exhaust valves. Some of these troubles may be confined to one or two cylinders.

If an engine pings objectionably because of too low octane fuel, retard the spark setting but first be sure that the cooling system is in good condition, the mixture not too lean and the combustion chambers free of carbon deposit.

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