<VV> more spark plug questions

[Michael Kovacs]

I have the list to interpret the prefixes and suffixes of the AC plugs. Now I need opinions on extended plugs vs the standard Corvair recessed ones. More /less ping? Which run hotter?
   
   I also have used set of NGK BP4HS, Bosch WR8AP and Champion UL12Y &UL15Y. Used sets are only for testing.
   
   The problem I'm trying to solve is occasional heavy knock during light 1st gear acceleration and run on at shut down. This tells me I have something too hot in the engine. It does not knock during normal driving. I can experiment with colder plugs, but need to know which of the above is colder than an AC44.
   
  Modified 140 with deck cut and .032 copper seal. 


MIKE KOVACS