The small hole in this restrictor may become partially blocked and limit the amount of oil flow to the cylinder head. Eventually lack of lubrication may cause a camshaft journal to score its camshaft bore and seize.
Some engine builders drill the existing restrictor to .062? (1.575 mm) to increase oil flow to the cylinder head and camshaft. Providing all other oil clearances are with specifications, this procedure prevents seized camshafts.
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