I am just about ready to fire up a new 350 crate engine. Now my questions about zinc additives and high zinc oils. This is a flat tappet cam engine. What kind of break in oil and after the break in period what kind of oil do you reccomend. Also where to get it. I work with a couple of guys who have built a number of engines and they say they just use Castol GTX and have never had a problem. I have been advised by GM and some others to go with the higher zinc stuff. Thanks to all who can help me.......Rich