Dave: you're right, of course about the 68's. However I have a manifold vacuum retard unit (not advance), giving no advance at idle.This was a really crude attempt to burn more NOx gasses by raising the temperature of the exhaust. All this really did was to dump a lot of heat into the cooling system and making the engine run hotter (and lousier). This is why I want to move to an earlier advance unit. I'm a bit worried about removing vacuum advance altogether (but it appears not to affect the 68's)
