[ht4100]

You're right about the ZDDP content in current oils for use with flat-tappet camshafts. Last year, I built a 383 stroker for my 86 Camaro. I bought flat-tappet cam from comp cams and they recommend the use of Rotella T oil to properly lubricate the cam because of it's ZDDP content. There is also an article on this in HOT ROD magazine that goes in depth about it. Since I would assume the HT4100 has a flat-tappet cam, and with it's tendency to wear cams out, it would not be a bad idea to use Rotella T, although they have reformulated it in late 2006-early 2007 to contain less ZDDP, so who knows if it's good enough now. A bottle of Cam-break in, or engine oil supplement from your GM dealer would probably be a good idea to run in an HT4100 engine. I probably will start running it in mine also. I can also get Rotella T 10w-30 at a few shops here in town.