Complicated subject!

Basically, over the last 10-15 years, there has been a "perfect storm" of conditions contributing to this widespread problem. The three main ones:

> Detroit totally stopped using flat tappet camshaft, resulting in a loss of dependable, low-cost tappet and cam-blank suppliers

> The guys who knew how to make the above "for generations" are dying off

> ZDDP levels in oils have slowly been reduced. No law against ZDDP, but it isn't good for cats, and the EPA forces automakers to give long "low emissions" warranties

The fixes? Also multi-prong:

> Use oil with enough ZDDP (EG: Mobil 1 15W50, etc.) or an additive

> Use lifters with either a ceramic-composite face, or the 0.012" laser-drilled hole in the face

> Avoid long periods of idling

> Don't go crazy with valve spring pressure. If "enough is enough", "too much" ISN'T better!

> And, most important: Assure that your new engine fires INSTANTLY (timing right, float bowls filled, shot of ether, etc.) and doesn't see under 2,500 RPM for the first 20 minutes or so.

Rick