What I took from it was that Zinc kind of eats into the lifters, and cam, and ten coats the parts. If you put to much then it does more harm than good. The old saying, if a little bit is good, then a lot is better. Don't get carried away with it.

Engine Oil Myths - GM TechLink: "A higher level of ZDP was good for flat-tappet valve-train scuffing and wear, but it turned out that more was not better. Although break-in scuffing was reduced by using more phosphorus, longer-term wear increased when phosphorus rose above 0.14%. And, at about 0.20% phosphorus, the ZDP started attacking the grain boundaries in the iron, resulting in camshaft spalling."

Excessive phosphorus (the antiwear component of ZDDP - Zinc DialkylDithioPhosphate) tends to cause camshaft spalling. 0.20% Phosphorus is the same as 2000 ppm of phosphorus. Phosphorus should not exceed 1400 ppm or 0.14% in engine oil for maximum wear protection, which is why the old API CI-4/SL 15W-40 HDEOs typically had 1300-1350 ppm of phosphorus.

It's better and cheaper to use an engine oil formulated with enough ZDDP than to mix your own by guessing at how much ZDDP to add. The new API CK-4 HDEOs typically have 1000-1200 ppm of phosphorus.

See Camshaft Spalling

So Valvoline VR1 is .14, should that be good? Was using conventional until this year when someone suggested to go with higher zinc amounts. Never had an issue with the conventional, but wanted extra protection and for the cost of $30 more per oil chance, it isn't too expensive. Change it twice a year. Conventional was .083 vs VR1's .14 according to Valvoline's site.

0.14% phosphorus is the maximum you should run in a engine that is broken-in. There's more to an engine oil that ZDDP content and I think Heavy Duty Engine Oils are better than racing oils for street use. See Corvair Oil Article.

Widman recommends HDEOs with higher phosphorus contents but a ZDDP manufacturer suggests that 1200 ppm is a good target. See ZDDPlus™ Tech Brief #2 – ZDDP and Cam Wear: Just Another Engine Oil Myth?.

I use Petro Canada Duron SHP 10W-30. It has 1200 ppm of phosphorus and have no problem getting 75 psi above 2000 RPM with my stock oil pump.

To get more life out of your engine, see Engine Wear.