I have to admit that the scariest thing i have done is the start up and break in of an expensive rebuild that I assembled myself. I let it sit for a week and a half before I could get up the nerve to fire it up. It was a 235 with hydraulic lifters, and man did it clatter when I fired it up and kept it at between 1500 and 2500 rpms. It quieted down pretty quickly. Everything worked out fine. You just don't have any choice but to run it at that rpm for twenty minutes if you want the the new cam to survive.
