Cometic Lower Intake Manifold Gasket | Nissan RB25 2.5L | RB25DE / RB25DET | IR511060AFM
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Cometic Lower Intake Manifold Gasket – Nissan RB25 2.5L | RB25DE / RB25DET | IR511060AFM
Fits Nissan RB25DE and RB25DET engines only. Not compatible with RB20 or RB26 — the intake port size and manifold bolt pattern differ between RB engine variants. This is the lower intake manifold-to-cylinder head gasket — not the upper plenum-to-lower manifold gasket. Confirm which gasket your application requires before ordering.
Cometic IR511060AFM lower intake manifold gasket for the Nissan RB25 2.5L inline-6 engine (RB25DE and RB25DET). Seals the lower intake manifold to the cylinder head face — the critical sealing interface for intake vacuum integrity on the RB25 platform. 0.15 lbs. Ships fast across Canada and the US.
Lower Intake Manifold Gasket — Function and Replacement
The Nissan RB25 uses a two-piece intake manifold system: an upper plenum assembly and a lower intake manifold that bolts directly to the cylinder head. The lower intake manifold houses the individual intake runners for each cylinder and the injector mounting bosses. The lower intake manifold gasket seals the mating face between the lower manifold and the cylinder head, maintaining intake vacuum integrity across all six cylinders.
A failed or degraded lower intake manifold gasket causes unmetered air to enter the intake system (vacuum leak), resulting in: rough idle, lean air/fuel mixture errors, increased idle speed that cannot be corrected by the idle air controller, hesitation under light throttle, and potential lean misfire under load. On a turbocharged RB25DET, a lower intake manifold leak can also cause boost control instability as the ECU attempts to compensate for the unmetered air signal error.
When This Gasket Is Replaced
The lower intake manifold gasket is disturbed whenever the lower intake manifold is removed. Common RB25 scenarios requiring manifold removal:
- Fuel injector service: Cleaning, testing, or upgrading injectors requires lower manifold removal on the RB25.
- Head gasket replacement: Lower intake manifold removal is required as part of the cylinder head removal procedure on many RB25 builds.
- Intake port matching: Port matching the lower manifold to the cylinder head for performance builds.
- Aftermarket intake manifold installation: Any aftermarket lower intake manifold requires a new gasket at the head interface.
- Engine rebuild: Full gasket replacement as standard practice during engine rebuilds.
The OEM lower intake manifold gasket on the RB25 is a composite rubber/fibre unit that can harden, crack, and lose its sealing properties with age and heat cycling. Replacing with a Cometic unit provides improved sealing and longevity.
RB25 Applications
The IR511060AFM covers both RB25DE (naturally-aspirated) and RB25DET (turbocharged) variants of the 2.5L RB inline-6. Primary vehicle applications include: Nissan Skyline R33 GTS-t, 25GT, and 25GT-X; Nissan Skyline R34 25GT-t, 25GT, and 25GT-X; and Nissan Stagea WC34 with the RB25DET. Confirm your specific engine variant is RB25 — not RB20 or RB26 — before ordering.
RB25DE and RB25DET only — not for RB20 or RB26. Lower intake manifold-to-head gasket only — not the upper plenum gasket. Replace as part of any lower manifold removal service.
Specifications
- Brand: Cometic Gasket
- Part Number: IR511060AFM
- Type: Lower intake manifold gasket
- Application: Nissan RB25DE / RB25DET — 2.5L inline-6
- Not for: RB20, RB26
- Weight: 0.15 lbs