GMx Casting Question

[David D.]

So when you see a Cast Part, Water Pump for example, some have a GM1, or a GM2, or a GM5 etc....Cast on them.

What is the significance of these GMx markings?
Do these correlate to specific time periods?
Do these correlate to Original vs. Over the counter products?

Thanks,
David

[Jack H.]

Re: GMx Casting Question

GM cast parts in different producing locations and often had more than one physical casting mold. The numbers you mention are for source traceability allowing production engineers to back track to the source/site/mold that created a specific part...

[David D.]

Re: GMx Casting Question

Jack,
Thanks. Do you know if any specific GMx number(s) were used on our Corvettes? Or were any and all of the GMx numbers up for grabs when it came time for assembly?
David

[William C.]

Re: GMx Casting Question

Anything that come down to Flint on the Truck from Saginaw was used for smallblock Corvette engines.

[Joe L.]

Re: GMx Casting Question

Jack,
Thanks. Do you know if any specific GMx number(s) were used on our Corvettes? Or were any and all of the GMx numbers up for grabs when it came time for assembly?
David

David-----

The numbers you describe were PATTERN numbers. For sand castings, patterns are used to make the sand molds from which the parts are actually cast. Over time, patterns may be replaced or added if production requirements indicate such a need.

For example, a pattern with the number "GM1" for a '608' waterpump was likely used when the '608' waterpumps were first released for 1961. For how long that, particular, pattern was used, who knows? However, let's say that it was last used during the 1965 model year and subsequently scrapped for whatever reason. In that case, no 1966-70 Corvette or any other Chevrolet small block was ever built with a pump that had a "GM1" pattern number on it. So, in this sense, pattern numbers MIGHT be related to certain time periods. No one has any of this information, though, and the only way I can see it could be determined would be through foundry documents. Of course, the casting DATE on a waterpump, for those units which are dated, is a much better determinant of whether a particular pump is "correct" for any particular engine.

The MOST that could be said when observing a known-original waterpump (or, any other casting) on a known-original engine is that a particular pattern number was being used at the time that engine was built. This says NOTHING about what other patterns were being used at that time, when that pattern was first used or when that pattern was last used. For example, the pattern number on the known-original waterpump from my 1969 small block is "GM 27". The ONLY thing that tells us is that the "GM 27" pattern number was being used for '608' waterpumps at the time my engine was manufactured in August, 1969. It DOES NOT tell us that was the only pattern being used.

[Roy B.]

Re: GMx Casting Question


GM dint use (1) sand castings mold , on the same run they may have had (15) molds going at the same TIME so if mold GM3 got screwed up they had back up molds. 2-3-13 or what ever!