DON'T do the oiling mod unless the engine is apart for rebuild. You won't believe the way that cast iron splinters when you drill and tap it. No matter how careful you are, there's NO WAY you could do it without getting metal frags into the oil passages, and that could kill your motor in short order.

The only time to do it is when you have a bare block on an engine stand, and can clean all the passages with brushes afterward. Doing it on an assembled engine will probably do more harm than good.

Bob
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