Recently finished a 396 motor and have run in the break in oil for a couple of hundred miles. I am questioning the need to add a zink additive for the next oil change. Obviously running a flat tappit cam and I used motor oil that included zink for break in. Valvoline makes a racing oil that includes zink and I am considering that for the next change. I have read articles for both sides of the use of oil including zink or adding a zink additive to just using regular motor oil. Somewhat confusing.