Genuine GM Parts 25161284 - Bypass Valve

Understanding bypass valve locations:

Factory assembled 454 and 502 engines and short blocks have two bypass valves installed in the block. These factory installed bypass valves (part number 25013759) will open at an 11psi pressure differential. One bypass valve is installed in the center hole on the oil filter pad (#4 in the picture located above). This hole is the oil return passage from the oil filter. The second bypass valve is installed in the adjacent hole (#3). The egg shaped hole is the high pressure oil supply passage from the oil pump.

For all racing applications that will NOT use an oil cooler but will maintain the stock oil filter location, you must remove the center bypass valve in location #4. Removing this valve eliminates three right turns in the oil system. However, if you leave this bypass valve in place the oil system will still function as it was intended, but a loss of oil pressure can result from the four right angle turns required for oil to return to the main oil tunnel.

If you intend to use a remote oil filter, a high pressure bypass valve, part number 25161284, must be installed in position #3. This valve will open at a 30psi pressure differential rather than the factory 11psi differential. A plug will be installed in position #4 to prevent oil flow through this passage. Oil should be returned to the block through the 3/8" hole located just above the filter pad.

If you intend to maintain the stock filter location and will use the factory provided oil cooler passages to install your oil cooler, then you must install two high pressure bypass valves , one in location #3 and one in location #4.