what kind of oil for new rebuild

The true synthetic is a superior oil for the reasons most understand however, one of the inherant problems is that synthetic is so slippery, when compared to conventional, that the lifters don't always rotate in their bores(roller lifters not included LOL). This rotation needs to occur so that the cam lobes are always seeing a nice flat area and that any wear to the bottom of the lifter is universal. Another problem I've heard is that if you use synthetic on a new engine build there is a possibility that the rings won't seat to the cylinder walls. Years ago alot of the north american car companies have said not to use synthetics until the engine has 10K on it but I don't think that is a concern nowadays.

Terry