If you want to stick to a multi, Valvoline VR1 20W-50 seems to be the current best choice. It has the high level of ZDDP you need for the flat tappet engine. The Rotella still has the ZDDP in the straight 30 and 40 weights as well. For a very complete discussion, check out CorrectCraftFan.com and do a search for either the VR1, Rotella or ZDDP oil.....lots of tech talk over there.
1991 ProStar 190—Acme 475, GT40-P heads, Edelbrock Performer intake, Mallory YLM Ignition
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