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Question Answered: Engine Catter at startup
March 18, 2012, 07:13 AM
Just about every factory GM motor after the mid 80s came equipped with hyperreutectic pistons, these pistons are an aluminum alloy with a high silicon make up, the piston do not reach true size in the cylinder until they build up some heat and come up to operating temperature, as a result the make a noise very similar to a rod knock, the noise is actually a cold undersize piston slapping against the cylinder wall, ive read in many articles that this short perion of slapping will not harm the piston or the rest of the motor for that matter
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