Buggin', not detonation ( that puts holes in ur pistons) but pre-ignition.
If the mill is older you might have losts of carbon in the chambers. The carbon acts as a hot spot, helping cause the pre-ignition. I've never used it, but I hear good things about a slime called Seafoam, which is poured into the carb while running.
Item second, while you were checking the distributor, did you check to see how the mechanical advance comes in? Check it. It may be happening too soon or in a totally non-linear fashion due to someone moneying with it who shouldn't have.
Item 3, try full mani vacuum to the vacuum advance. ( use ported for emmissions testing though). A simple test and I believe you'll find it helps the pre-ignition problem and might give you more power as well.
When you spin a rod bearing, at least the few unfortunate one I have, it "on" all the time. Not load related. Main bearings are load related and have more of a thump, than a clack. then theres wrist pins, etc.
Pre-ignition sounds like someone playing the "spoons" under the hood.
Good luck man.
67 Chevelle SS 427/L88
[This message has been edited by 427TRI (edited 08-21-2000).]