Altho 140c (284f) is hotter than I'd like to see, I don't think it is too hot--your smoke probably result of hot engine,excessive manifold vacume from backing down as you came off track and
oil down the valve guides as motor cooled off
I have seen several of the LS engines come thru our shop that had crushed skirts, broken ring lands and valve guide clearance uo to .006 inch.All the engines with these symphons smoked
Jerry