Upper Intake Manifold with Gasket for Chevrolet Monte Carlo (1998-2005) 3.8L

Direct-Fit Replacement Upper Intake Manifold with Gasket for 1998-2005 Chevrolet Monte Carlo (W-Body)

What it Does: The upper intake manifold kit replaces the degraded factory composite plenum on the 1998-2005 Chevrolet Monte Carlo to eliminate vacuum leaks and prevent coolant intrusion into the combustion chambers.

The Stock Chevrolet Monte Carlo Intake Plenum Failure

Factory composite nylon upper intake plenums on the GM 3800 Series II (L36) engine suffer a well-documented failure point adjacent to the Exhaust Gas Recirculation (EGR) stovepipe. Continuous thermal cycling from localized exhaust gas heat breaks down the thin composite partition separating the plenum runners from internal coolant passages. Over time, the plastic softens, warps, and micro-fractures, allowing pressurized coolant to bleed into the lower intake and intake ports. This leads to unmetered air leaks, poor idle control, misfires, and catastrophic hydrostatic lock if left unaddressed.

The Engineering Solution

Designed as a heavy-duty service replacement, this intake plenum features a reinforced, heat-stabilized composite structure engineered to resist thermal degradation and warping around high-temperature exhaust passages. The internal air runners are molded to factory specifications to preserve laminar airflow dynamics, throttle response, and manifold absolute pressure (MAP) signal integrity. Each kit includes a direct-fit port gasket lined with elastomeric sealing beads to prevent blowout under engine vacuum, paired with replacement throttle body studs, fuel pressure regulator springs, and precision O-rings to ensure a leak-free seal across the W-Body engine bay.

What's Included

• 1 Upper Intake Manifold (plastic)
• 1 Upper Intake Manifold Gasket with port seals
• Fuel pressure regulator spring
• Throttle body studs
• O-rings and fittings as pictured

Technical Specifications

Compatibility

• Monte Carlo 3.8L Gas Naturally Aspirated — 1998-2005
• Monte Carlo 3.8L Gas Supercharged — 2004

Frequently Asked Questions & Fitment Warnings

Does this fit the W-Body Monte Carlo?

Yes, this is a direct fit for the 1998-2005 Chevrolet Monte Carlo equipped with the GM 3800 Series II 3.8L V6 engine. This kit does not fit Monte Carlo models equipped with 3.1L, 3.4L, or 5.3L V8 engines.

What is the proper fastener torque sequence for this manifold?

Install on a completely cool engine and torque manifold bolts in factory sequence to 89 in-lbs (10 Nm) to avoid warping the composite flange.

The Chevrolet Caliber

Protect the legendary longevity of your front-drive GM coupe with precision-molded induction hardware built to deliver dependable vacuum integrity and everyday power.