DATZ

If you’re running dished pistons you have no quench.

It’s an open chamber cylinder head. There is no quench.

The bypass is there to supply coolant to the intake manifold during cold start ups. Nissan never installed them in Z’s shipped to Australia. Tony is wrong and doesn’t know what he’s talking about.

The only Z heads that have any quench (“squish”) are the P79/P90/p90a. The E31, E88, N42, N47 have Zero quench regardless of the piston. If quench isn’t perfect, you don’t want it.

It’s hilarious how everyone throws out the term “quench”. This head has the best quench”, “if you do this, you’ll get more quench”…. Here’s the rule: if quench isn’t perfect, YOU DON’T WANT IT! When you’re raising compression, Quench is the primary cause of detonation - when it’s not perfect. There is ZERO quench pad on the E31, E88’s, N42, N47. The P-79, P-90 and MN-47 all have quench pads. The E31, E88, N42 and N47 are considered “Open” Combustion Chambers; Where the P-79, P-90 and MN-47 are considered “Closed” combustion chambers. “Open” combustion chambers have little to no quench pads. The reality is, none of the Z heads have great “quench.” So don’t worry about it. Now that’s not to say BPE Heads, Rebello’s…. Can’t weld up any of these heads and create perfect quench. It’ll just cost you money.