" From: farna@xxxxxxx " " I don't know the measurements off the top of my head, but the cylinder walls are much thicker than the 360 and 401. It can be safely bored 0.060 over, I think. more than that i think. met a fellow with a '309' in his american at one of our shows last year - 290 bored out for 4.0 slugs, ~0.125" over. ________________________________________________________________________ Andrew Hay the genius nature internet rambler is to see what all have seen adh@xxxxxxxxxxxxxxxxx and think what none thought