CNRAQR LS Engine Oil Cooler Bypass Cover Block Off Plate for Gen III/IV LS Small-Block — Black Anodized 6061-T6 Aluminum, Gasketed

CNRAQR's LS engine oil cooler bypass cover block off plate replaces the original GM part with a CNC-machined 6061-T6 aluminum cap that seals off oil cooler ports on Gen III/IV LS small-block pans without sensor holes.

When removing or blocking an oil cooler line on many GM LS-series engines, you need a durable, leak-resistant replacement that matches the pan's port location above the oil filter. This CNRAQR kit is built as a direct-fit upgrade to OE#12577903, offering a smoother internal cavity for better flow, corrosion-resistant hardware, and a bonded high-temperature gasket. It ships as a complete set ready for installation on compatible LS small-block oil pans.

Will this block off plate fit my Gen III or Gen IV LS oil pan?

Compatibility is focused on LS small-block pans where the oil cooler ports are positioned above the oil filter. It’s intended as an upgraded replacement for OE GM part number 12577903, but you should verify port placement and bolt pattern against your pan before purchasing.

• Designed for GM Gen III and Gen IV LS-series small-block oil pans with ports above the oil filter.
• Matches the bolt pattern and port location of the OE#12577903 style covers.
• Measure your pan port spacing and compare to product dimensions (2.70 x 1.10 x 0.75 inch).

How is this bypass cover built and what materials are used?

The cover is CNC-machined from 6061-T6 billet aluminum for rigidity and precision, then anodized for corrosion resistance. Its internal cavity is smoothed and ported to reduce turbulence compared with typical diecast OE covers, and the kit includes zinc-plated hardware and an upgraded FKM rubber-to-aluminum gasket.

• 6061-T6 billet aluminum construction for strength and heat resistance.
• Black anodized finish protects against corrosion and wear.
• High-temp FKM rubber bonded to aluminum gasket for leak prevention.
• Zinc-plated steel flanged hex head screws included for secure mounting.

What’s included and how simple is installation?

The package contains two bypass covers, four mounting screws, four plugs, and two upgraded gaskets so you can service both sides or keep a spare. Installation is straightforward: align the gasket, place the cover over the pan port, and tighten the supplied screws to proper torque—no additional machining or special adapters required for matching pans.

• Kit includes: 2 covers, 4 screws, 4 plugs, and 2 bonded gaskets.
• Pre-threaded holes and hardware allow bolt-on installation with common hand tools.
• No sensor ports on this version—confirm you don’t require sensor accommodations.
• Follow torque specs for your engine or use a thread locker where appropriate.

What performance or maintenance benefits can I expect?

This block-off cover provides a robust, leak-resistant seal while removing the stock oil cooler path, useful for engines converted away from external coolers. The smoother machined cavity can reduce flow disturbances and the anodized billet resists corrosion for longer service life than many diecast OEM covers.

• Improved sealing with high-temp bonded gasket reduces oil leaks.
• Billet construction withstands heat and stress better than cast parts.
• Smoother internal contours can improve internal oil flow behavior.
• Complete hardware means one-stop replacement without sourcing extras.

Who is this for: The CNRAQR LS oil cooler bypass cover is aimed at technicians, engine builders, and DIY enthusiasts working on GM Gen III/IV LS small-block engines that no longer use the factory oil cooler or need a sealed replacement for the OE#12577903 cover. Confirm port location and the absence of required sensor ports before buying. CNRAQR offers a two-month return policy and customer support for product questions.