A valley pan gasket set seals the valley pan or lifter valley cover on V-type engines. A leak here can let oil escape at the back of the engine or allow unmetered air into the intake.
Use the Evergreen eCatalog to look up the correct valley pan gasket set by vehicle or engine. Always verify the part number and application before ordering. Evergreen sells through authorized wholesale distributors; see where to buy or become a wholesale partner.