the spun bearing was my old engine (ls1) which i bought second hand, as a bit of an unknown quantity. i put a cam, new chain/sprockets etc and arp rod bolts in and fitted a dry sump, and did 3 trackdays before it span a bearing, and was using 6500rpm. 2 bearings picked up and marked the crank quite badly.
i then ended up with a weber race engine from the states with a forged LS6 bottom end when the dollar was poor against the £ for a bargain price! currently using that with my ls1 heads on etc.
touch wood the engine seems to be fine and working ok now.