have been working on a 750-4 than a buddy bought this morning.Personally I own a CB750 K6.While working on this one, so many thing are differant. I saw that the manufacture date is 4-70, but everything I see says sandcast. I got the engine number cb750e-1033080. Could this be a sandcast engine in a later frame or a left-over from the factory or was a few made at this late date? Please ,someone tell me.