FAST 146203-8 LSXR 102mm Intake Port Seals for LS1/LS6/LS7 Cathedral Port (8pc)

Vehicle Fitment

• GM LS-based engines: LS1, LS6, LS7 (cathedral port cylinder heads) - fitment is engine-specific, not vehicle-year specific; applicable across any chassis running these engines with a FAST LSXR or LSXRT 102mm intake manifold

Fitment Notes

• Requires a FAST LSXR or LSXRT 102mm intake manifold - not a direct fit for factory GM cathedral-port intakes without the FAST manifold
• Not compatible with LS3 applications (LS3 requires FAST part 146003-1 or 146003-8 instead)
• Does not include the upper intake manifold plenum gasket - port seals only

Features

• Buna rubber construction for resistance to heat, fuel, and oil exposure
• Cathedral port profile matched to LS1/LS6/LS7 cylinder head geometry
• Direct O-ring style replacement seal for FAST LSXR/LSXRT intake manifolds
• Engineered specifically for the FAST LSXR 102mm manifold platform
• Seals the intake runner-to-cylinder-head interface to prevent vacuum and air leaks
• Sold as a complete matched set for full 8-cylinder coverage
• Maintains consistent manifold sealing under normal engine vacuum conditions
• Simple bolt-in replacement for worn or aging factory-style seals

Specifications

• Manufacturer Part Number: 146203-8
• UPC: 036584203704
• Material: Buna rubber
• Port Style: Cathedral
• Quantity: Set of 8
• Upper Intake Manifold Plenum Gasket Included: No
• Package Dimensions: 5.75"W x 1.5"H x 9.5"L
• Shipping Weight: 1.0 lbs

Included Components

• 8x Intake Port Seals (Buna rubber, cathedral port)

Product Description

The FAST 146203-8 seal set replaces the eight port seals that mount between a FAST LSXR or LSXRT 102mm intake manifold and the cylinder heads on LS1, LS6, and LS7 cathedral-port engines. These seals form the critical air-sealing barrier at each intake runner opening, and over time heat cycling and fuel exposure can cause the factory Buna rubber to harden or shrink, leading to vacuum leaks, rough idle, or inconsistent air/fuel ratios across cylinders.

Because this set is designed specifically around the FAST LSXR/LSXRT manifold's port geometry, it is not a universal cathedral-port gasket - it will not properly seal on a stock GM cathedral-port intake or on LS3 rectangular-port applications, which use a different FAST part number. Installers should confirm their intake manifold is a genuine FAST LSXR/LSXRT unit before ordering.

This is a seals-only kit; it does not include the separate upper intake manifold plenum gasket, so builders doing a full manifold reseal should budget for that gasket separately. At roughly $44 and shipping as a compact 1 lb package, it's a low-cost maintenance item for anyone running a FAST LSXR-equipped LS1, LS6, or LS7 build who's chasing a vacuum leak or doing preventive maintenance during a manifold R&R.