Improved Racing LS Rear Passage Plug Billet 6061-T6 Aluminum for GM Gen III & IV, Double O-Ring Seal

The Improved Racing GM Gen III & IV LS Billet Rear Passage Plug Oil Diverter Barbell is a direct-replacement aluminum plug that prevents unfiltered oil from bypassing the filter and seals the rear oil gallery on LS engines.

When upgrading or maintaining GM LS Gen III and IV engines, the stock plastic rear barbell plug can allow contaminated oil to leak past the filter gallery over time. This CNC-machined billet 6061-T6 aluminum diverter replaces the OEM plastic piece with a durable, double-O-ring sealed component, engineered to resist heat, crush, and long-term degradation. It’s designed for fitment without modification and includes a removable-thread feature to make future service easier.

How does this billet barbell stop dirty oil from bypassing the filter?

The Improved Racing diverter isolates the rear oil passage with a precision-machined bore and two Viton O-rings that create a positive seal. The result is a secure barrier that keeps oil flowing through the filter instead of escaping around a weakened plastic plug.

• Double O-ring configuration for redundant sealing
• 6061-T6 billet aluminum resists deformation and heat
• Exact replacement dimensions for GM LS Gen III & IV OEM locations

Will this part fit my GM Gen III or Gen IV LS engine without modification?

Yes — the plug is manufactured to match the OEM barbell dimensions so it installs in the same rear oil gallery location. No machining or block alterations are required for standard Gen III and Gen IV blocks.

• Direct drop-in replacement for factory plastic barbell
• Threaded M4x0.7 removal hole for safe extraction if needed
• Designed for common LS blocks from GM without adapters

What materials and design features improve long-term reliability?

The unit is CNC machined from aircraft-grade 6061-T6 aluminum and uses heat-resistant Viton O-rings, giving far greater longevity than the original plastic. Combined with the double O-ring layout and a corrosion-resistant finish, the diverter stands up to thermal cycling and oil exposure.

• Billet 6061-T6 aluminum body for strength and thermal stability
• Viton O-rings for oil and heat resistance
• Precision machining for consistent sealing and alignment

How does the threaded removal feature help during maintenance?

The integrated M4x0.7 threaded hole lets technicians or DIYers use a small driver or bolt to pull the plug without damaging the block or surrounding parts. That feature simplifies service and reduces the risk of breakage during extraction.

• M4x0.7 thread accepts common fasteners for extraction
• Prevents prying or block-scratching during removal
• Speeds up routine service and inspections

Who is this for? The Improved Racing GM Gen III & IV LS Billet Rear Passage Plug Oil Diverter Barbell is aimed at performance builders, engine rebuilers, and enthusiasts who want a long-lasting alternative to the stock plastic plug. If you’re maintaining a GM LS engine, building a high-mileage daily driver, or upgrading for reliability under increased heat and stress, this billet diverter offers a durable, service-friendly solution that preserves oil flow routing and reduces the chance of bypassed filtration. Made in the USA and ready to install in standard Gen III and Gen IV LS rear oil galleries.

• Improves oil flow and prevents unfiltered oil from bypassing the filter
• Double O-ring design ensures a positive seal in the oil gallery
• Direct replacement for the OEM plastic barbell on GM LS Gen III & IV
• CNC-machined from billet 6061-T6 aluminum with durable Viton O-rings
• Threaded M4x0.7 extraction hole for easy removal
• Manufactured in the USA