Versions
The Z32's (or, more specifically, the VG30DE/TT's) cylinder heads are made from cast aluminum. They feature 24 valves (4 valves per cylinder) with self-adjusting hydraulic valve lifters. The turbo models featured inconnel exhaust valves to withstand hotter exhaust gasses.
There were a few different versions of cylinder heads put in the Z32.


Phase I
90-92 (30P)
90-94 (40P)
Phase II
93-96 (10Y)
95-96 (48P)

Generally speaking, the TT heads flow better than NA heads and can be considered an upgrade if installed on an NA, albeit a minor one. The 48P (late-style) TT heads also had a slightly casting change which flowed even better than the 40Ps. There is also a difference in "old style" (P1) and "new style" (P2) heads. As the P1 and P2 shift marked a change in fuel injector design, the fuel rail had to change. This meant the lower intake manifolds had to change, and the ports on the intake side of the heads changed as well. For this reason, new style intakes are incompatible with old-style heads, and vice-versa. The proper way to install P2 injectors on a P1 motor is to either have the lower intake manifold machined to accept the P2 fuel rail, use an aftermarket fuel rail, or simply use a Deatschwerks-style adapter kit.