Rear Catalytic Converter - 1991 300ZX

When hunting Nissan 300ZX Twin Turbo rear catalytic converters in the junkyard, restrict searches to 1990-1996 VG30DETT donor cars only—naturally aspirated VG30DE models utilize different Y-pipe geometry that will not seal. The critical OEM Nissan part numbers are 20802-40P00 for early Federal cars and 20802-40P02 for California emissions packages. Always verify the oxygen sensor boss locations before purchase; 1991 models feature a single upstream bung while later cars added downstream monitoring. Shake the converter vigorously—rattling indicates substrate disintegration, a common failure mode when turbo seal failures dump oil into the exhaust stream or running rich melts the brick. During extraction, apply heat to the Y-pipe flange nuts and use six-point sockets to avoid rounding the M8 studs seized in the aluminum collector. Replace the donut gasket (20692-40P00) and inspect the flex joint for stress cracking. Note that JDM Fairlady Z VG30DETT models typically omit this rear catalytic converter entirely, featuring only the front pre-cats in the turbo downpipes.