I have about 30 four cylinder engines and it is my observation that 1922-24 Stars used the W4 with round plugs in the water jacket and a slip fit, rear dump manifold. The 25-early 27 used the W5 with bolted plates on the water jacket and a rear dump manifold with threaded jam nut. Later 27 Stars went to rubber engine mounts, side mount steering box, and a front dump manifold with threaded jam nut. About when Durant started production again they used the W5 and reverted back to round water jacket plugs, and front dump manifold with threaded jam nut.