[blykins]

Chas,

It depends on the journal size.

Most of the bearing manufacturers tell you to be at about .001"/inch of journal, and you add a half thou for the "hipo" stuff.

My SBC rod journals are usually at around .0020-.0025". BBC journals are the same.

Cleveland, SVO, and FE main journals are around .0027-.003".

My BBF and Windsor stuff is around .003" on the mains. If it's a few tenths each direction, I don't sweat it.

Cup engines run really tight clearances (they are pretty small journal though) and you know what kind of rpms they pull.

There has always been a tendency to start opening up the clearances when "race" is written in front of "engine", but I've never really seen the need.