If you have lifters tapping try the tranny fluid idea before your next oil change. Don't verfill your engine by adding a quart of tranny fluid, but if 1 quart won't overfill it go ahead and add it before you change your oil next time. It's ok to drive with it in there and shouldn't hurt anything. Tranny fluid will help to clean everything out and may help with lifter tapping. I know this works because I have done this on an 85 Ford van with a 302 in it. It had serious lifter tapping in it and it made a big difference.
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