My interest is in the 318, but I think this also applies to the slant. And I think there have been posts here in the distant past about limiting total centrifical advance by closing the slot in the distributor plate.

Is there a percieved or real need to limit the max advance in these engines today because:

a) engines that have been rebuilt with hot / performance cams or increase comp. ratio idle better with more advance, and hence the top-end advance needs to be brought down to limit ping, or

b) engines that are original or otherwise have been rebuilt to stock specs are pinging too much on today's gas, and also (maybe) like to have 10 - 20 degrees BTDC to idle better, and the original max advance needs to come down?