dual spark heads
If I remember right the earlier dual spark plug system used on production vehicles was more for emission than for performance....I remember an 86 Datsun used them on the 4 cylinder engine.....The plug on the intake side was for combustion and the one on the exhaust was used to help with the burning of exhaust gases....No performance gains...The Rangers that used that on the 2.3-2.5 4 cylinders were slugs.....
