Part number vs. Casting number

[Justin S.]

Can someone please explain the purpose and value of a casting number to the end user?
1. I've never referenced a casting number at a parts house
2. Why would GM create a cast numbering convention so close sequentially to the part number and not instead use a casting mark?

Justin

[Joe L.]

Re: Part number vs. Casting number

Can someone please explain the purpose and value of a casting number to the end user?
1. I've never referenced a casting number at a parts house
2. Why would GM create a cast numbering convention so close sequentially to the part number and not instead use a casting mark?

Justin

Justin------


A casting number (or, forging number) is the GM part number for the casting (or forging) and is primarily used for internal GM manufacturing purposes. The raw casting/forging is very rarely available in SERVICE. After the raw casting is manufactured into a finished part, the finished part is usually assigned a different finished part number (which very often appears nowhere on the part). This is the part number used in PRODUCTION and available in SERVICE.

Sometimes a finished part number can be identified from a casting/forging number and often it's the only number found on the part. This can be tricky, though, since sometimes more than one finished part is manufactured from a particular casting/forging.

Sometimes, a casting/forging number and finished part number are the same. Why this occurs I do not know.

[Duke W.]

Re: Part number vs. Casting number

A couple of examples:

Brake drums used for both standard and metallic brake were usually the same casting number, but those destined for metallic brakes had a finer surface finish and a different finished part number. IIRC the '63-'64 front drum casting numbers were the same, but those destined for metallic brakes actually had a slightly thicker web stamped with an "X".

The number that is molded into camshaft castings is the actual part number of the finished camshaft, like 3736098 for the Duntov cam. What was sold over the counter was an "assembly" of camshaft and indexing pin, and the Duntov was 3736097. Sometimes casting/forging numbers and the finished camshaft number are referred to as the "ID number" in parts catalogs.

These part numbers are the same as the GM drawing numbers, whether for a single part or an assembly. The ...098 drawing shows all the detailed data for the finished Duntov cam lobes along with the data for the "as cast" lobes and refers to other drawings for most other dimensions since the journals and other dimensions were mostly the same as other existing camshafts. The ...097 drawing is a simple A-size drawing showing the pin and its part number and front of the camshaft.

Whether or not these numbers were sequential or not depended on how the drawings were queued up for the release process. In the case of camshafts, some are and some are not, but fairly close.

The casting/forging number is useful to restorers if you are looking for original parts or want to "upgrade". For example the '63 rear axle shaft drive flange was cast and weak, and in some cases can cause u-joint grounding. Later parts, and there were two, were forged and of different geometry making u-joint grounding less likely and they were also stronger, even though some sections were thinner because they started out as forgings. So if restoring a '63, depending on your objectives, you can either go with the original part or the better later parts.

Duke

[Kenneth B.]

Re: Part number vs. Casting number

Each part of a assembly has a part #. when a part is assembeld it is given a part #. Each part including castings were manafactured at many plants & not all at GM plants.Drawings were made bids were taken from each supplier by each part #.Some assembelys were purched from a supplier who sorced some parts out, assembeled & sold the finished assembly to GM.