what does this casting # mean? 40088730-318 3

Cast on the side of the block, drivers side.

casting #
CID
third revision of the mold when casting

Ok so what year does the # make it?

Quote:

---

Ok so what year does the # make it?

---

that casting number was used for multiple years of the 318 after 73 or 74 , the date the engine was cast is on the side of the engine just like that number you posted , plus under the drivers side head there will be a stamped number that will tell you when it was assembled.