Discussion
In short concise terms piston slap is the noise produced when the piston hits the cylinder wall. Normaly almost instantly as the cylinder fires at the top(ish) of its stroke.
Normal cause is the piston/rings is/are worn allowing movement when the piston is underpressure i.e it is no longer a correct fit in the bore. Under extreme circumstances it can be because the piston has been 'ovaled' or damaged due to excessive boost in a force inducted engine. Or it can simply be due to the normal wear and tear on a high mileage engine. Either way its likely to lead quite quickly to a dead engine. The only exception to this is an engine with forged pistons when started from cold. Due the thermal expansion properties of a forged piston over a cast one (i.e. they expand more) they have to machined smalled so when hot they expand to fit. Hence their will be a touch of slap from cold.
Hope this helps.
Matt
Normal cause is the piston/rings is/are worn allowing movement when the piston is underpressure i.e it is no longer a correct fit in the bore. Under extreme circumstances it can be because the piston has been 'ovaled' or damaged due to excessive boost in a force inducted engine. Or it can simply be due to the normal wear and tear on a high mileage engine. Either way its likely to lead quite quickly to a dead engine. The only exception to this is an engine with forged pistons when started from cold. Due the thermal expansion properties of a forged piston over a cast one (i.e. they expand more) they have to machined smalled so when hot they expand to fit. Hence their will be a touch of slap from cold.
Hope this helps.
Matt
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