I'm trying to figure out which head is better for my 280zx NA. Currently i have a N42 on there, and it is good, but I want one with the highcompression. As well as any otehr information about the two that is useful. Thanx
Both offer the same compression on a 280ZX bottom end, 9.8:1,
pretty good! Differences are: N47 has the dreaded round exhaust ports and flow-restrictive liners, probably not much of an issue for a street car, but you would need a different exhaust manifold to use the N47. The N42 has softer valve seats, but I've run one for years on my 3.1, put ~20,000 miles on it and ~35 track days, and the valves aren't sinking. Stick with the N42.