actually, quad cams are the wrong terminology being used.
whether an engine is DOHC or SOHC is purely dependant on how many
cams are operating above each bank of pistons.
the quad cam term was hatched because since there are 2 cylinder
banks, for eg, on V engines and boxer engines, there are
effectively 4 pieces of cams altogether. however, since there are
only 2 cams over each bank of cylinders, these engines should be
collectively described as DOHC engines. 
