The 2JZ engine is a renowned powerplant in the tuner world and is responsible for the Supra's popularity in its last year. On stock internals, the over-engineered, closed-deck engine architecture allows for massive quantities of boost while still staying strong.
This, paired with the inherent dependability of any inline-six engine, is mostly the reason for the 2JZ's capacity to survive so much power, but the only way to understand how Toyota engineered the 2JZ to be so strong is to learn more about this engine.
Because of the two overhead cams, each cylinder has four valves for improved air/fuel mixture and flow, as well as a top plug arrangement for optimum spark.
Bucket type lifters sit on the lobes of the camshaft, and although this doesn't allow for very aggressive cams, it helps enhance engine dependability by lowering the number of moving components.
MLS Head Gasket
Toyota employed a multi-layered steel head gasket for this engine, which decreases the risk of it blowing.
MLS head gaskets are used on high-powered engines due to their inherent strength.
A closed deck is when the cylinder bored are braced at the top where the cylinder head attaches and rests on. In comparison, an open deck engine is a "floating cylinder" design where it is only braced from the bottom of the cylinder liner.
Closed deck engines are much stronger and resist cylinder liner shifting and movement, increasing reliability and durability of the engine considerably.
Toyota attached a reinforcing girdle to the bottom of the 2JZ to provide strength while still enabling access to the crankshaft. A girdle increases strength and prevents unwanted movement and shifting.
Finally, the crankshaft is virtually unbreakable thanks to a forged crankshaft and large bearing design.