Inside the LS engine sits a part, and no one knows its proper name. This strang piece has often been referred to as a passage plug, dog bone, barbell, and rear oil galley plug. And while we’re not even sure what the correct name is, we can tell you that this factory plastic piece plays a critical role in the Gen III and GEN IV LS engines. 

The OEM LS barbell, or whatever you want to call it, is installed in the block and diverts dirty oil in the engine through the oil filter before sending it back to the bearings and lifters. As this part ages, the problem is that it can allow dirty engine oil to bypass the oil filter and contaminate the lifters and bearings, leading to parts failure. However, Moroso has recently introduced a new design that is much more durable and efficient than the factory plastic part. 

Moroso’s LS oil galley diverter (PN 25030) — there’s another name for it — is perfect for replacing an old worn out unit in your LS engine that can allow dirty engine oil to bypass the oil filter. And instead of plastic, Moroso machines its part of billet aluminum for superb durability, unlike the OEM part (PN 2573460). But a material change to this part is not the only difference. The company also improved on the design, adding a secondary o-ring to seal off dirty oil and ensuring that it goes through the filter first before being diverted to the bearings and lifter. Other benefits to the Moroso oil galley diverter include minimized flow restriction due to its smaller shaft size, Viton constructed o-rings that can withstand any engine oil, and can be removed easily from the engine block thanks to a handy 4mm threaded hole. 

Fits GM Gen III & IV LS Engines 4.8L 5.3L 6.0L 6.2L (Including Vortec Truck Engines)

• Replaces a worn out or old rear oil passage plug that could be allowing dirty engine oil to bypass the oil filter
• Machined out of billet aluminum, the OEM GM Part No.12573460 is constructed out of plastic
• Improved design with a secondary O-ring that’s function is to seal dirty oil from flowing to the engine bearings
• The shaft diameter of the Moroso passage plug, “Dogbone” or “Barbell,” is smaller than the OEM piece to minimize any flow restriction
• Supplied O-rings are constructed out of Viton to withstand all types of engine oils, compression cycles and have a high-temperature rating
• Can be easily removed from the engine block once installed with its 4mm threaded hole

For more information on this innovative part and others, be sure to check out Moroso.com.