I once had a Nissan VG30 that had compression on all cylinders while cranking, but one dropped to near zero while running. Being a bit dumbfounded, I changed the offending bank's cylinder head and fixed the problem. Now I suspect a lifter had a clogged bleed orfice and was thus pumping up and...
It might also be noted that Ford and Nissan produced dual-plug 4cylinder automotive engines. The Ford was a version of their SOHC 2.3L and IIRC the Nissan a 2.4L However, if it made such a huge difference, wouldn't everyone be building them by now?
Some extreme performance engines run dual...
