Brendan,
I looked around in various places for info on this subject. It was a hot item some time ago, but I think there is lots of Voodoo mixed in with it.
These are the conclusions I have come to;
Zinc in current motor oils was reduced, not removed.
Reduced zinc levels in modern gas engine oils can lead to premature cam failure when using aftermarket high lift cams in conjunction with high valve spring pressures.
These failures usually occur during a initial break in period as the lifters and cam wear into each other and high loads are developed.
Modern gas engine oils will not adversely affect flat tappet engines with stock valve train components and camshafts, especially after they are broken in properly.
Modern gas engine oils have no adverse affect on the stock engines usually seen on this site. Light spring pressures and mild cam grinds found in these engines perform fine with any modern day oil.
This is the deal as I see it!
Stuart
