I don't have the race experience of some other guys on this board, however I am an Amsoil fan. They make an oil called Z-Rod which as you may guess by the name, is aimed at flat tappet engines. An oil analysis I read at one point showed it had very high levels of zinc in(higher than VR1 and Joe Gibbs), it as well as some other additive that helps prevent corrosion during long term storage.