Three things cause ping.
The first (most common and easiest to fix) is that the timing too far
advanced for the compression ratio and octane rating of the gas being
used. Start by checking the timing with a timing light. If it is where
it is supposed to be, check that the vacuum advance is operating as
designed. Also check the mechanical advance. Directions for testing
can be found in your engines shop manual. Many years ago we used to set
timing by advancing until it pinged and then backing off just a bit.
Not the most scientific way to do it, but I didn't have a timing light.
The second cause of ping is some piece in the combustion chamber is not
being cooled enough and is igniting the fuel/air mix before the spark
plug has a chance to do so. An example might be a sharp edge caused by
a small screw someone dropped into the carb which eventually made its
way into the combustion chamber and lodged into the top surface of the
piston. It becomes very hot and as each compression stroke occurs
ignites the mixture in the cylinder prior to the spark plug. Saw this
occur many years ago when some un-named dumbass dropped a 6-32 screw
into the carb on a 312 Ford V8 I was working on.
The least likely cause is that the engine is running way too hot. This
could be caused by either a cooling system problem or because the carb
is set way too lean. It should show up on your temperature gauge. If
this were the case and allowed to continue the engine will not last
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