What is the purpose of the 2nd coil-4 Exhaust side spark plugs on a 1983 Nissan-Datsun 720 pickup with a 4 cylinder 8 spark plug engine?

you have 16 valves in stead of 8. 2 intake and 2 exhaust. they fire at different times to increase power. it's like haveing a V8 with less space.

wow, way wrong. The plugs on the exhaust side is for emissions. this way it fires on the exhaust stroke to help burn unspent fuel and gases before it goes out your exhaust pipe.