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There is a real nice yet little known test for piston slap I'll pass along. Some test results can be mixed or ambiguous but this one is 100% and I've never seen it wrong after using it for the last 10 years.
When the engine is cold, the aluminum piston is small in comparison to it's iron cylinder. Therefore the rather hollow slapping noise will be loudest first thing in the morning. After the engine warms up, the aluminum piston heats up faster than it's iron cylinder, cutting down on the excessive clearance between the piston and cylinder wall.
So, the test is this:
First thing in the morning, start the engine up and run it for 15 seconds while you listen carefully and memorize the sound and it's intensity. Shut it down quickly, pull the spark plugs and put two squirts of motor oil into each cylinder. Reinstall the plugs, fire the engine up again and listen.
If you have piston slap the noise will have been greatly reduced or even eliminated…..for 15 or 20 seconds that is, and then your nightmare noise will come back like a Marine Corps marching band coming toward you in the parade.
Thanks to Dave... from. http://remanufactured-engines.com/page5.htm
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∙ 16y ago
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