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Old 03-18-2019, 02:49 PM   #5
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Join Date: Oct 2014
Location: California Central Coast
Posts: 1,268
Looks to me to be an "oil fouled spark plug saver" type of device. The intent was to have a central port (the hole you see) for the spark plug to fire through, but prevent oil scraped from the cylinder walls from reaching the plug.
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