A cost effective alternative to the factory GM piece, these Valley Plates do not have the two provisions for knock sensors. These are usually not used in racing applications, as open headers, solid lifter cams and stiff suspensions can false trigger them. Also engines that are using a carburetor and distributor do not need the provisions for the knock sensors, which creates a cleaner installation. The aluminum construction of these valley plates weigh less than the factory cast piece. These can be used on factory and aftermarket GM LS Series style engine blocks.