Short Steering Arm Markings

[Iowa Jon]

Hi all,  I have some steering arms that I assumed were original from my 1969 Z28.  However i cannot read the part numbers that are left on either arm.  One is stamped HR? and TK?  Was there other GM cars that came with factory short steering arms?  I could not find a conversation about the marks on my arms.  Are these aftermarket?  I did see some repo's from CPP thought maybe these were repos.  I did media blast them this morning.  See picture.  Thanks

[boomer632]

I had one just like that. Has the HR and the casting numbers are there, but not legible. I compared it to another oem arm and it was exact match. I dont believe it was a repro, just poor casting numbers. Based on what I have seen with these short arms when looking to buy a set (for long time), I believe your arms are GM. I see that your numbers are unreadable, but in the correct location. 3954876 and 3954875 is what is most likely there.  The repros look nothing like the GM ones. GM ones have real wide parting lines and obvious grinding marks where the casting flash was removed like bottom photo shows.

[Iowa Jon]

Thanks Boomer,  I see what you mean by the parting lines and casting flash. I compared it to the repo's and now I see the differences.  Thought maybe they came off another GM car but I could not find any examples.  My disk brake brackets and shields still have the numbers on them but they look like they were repainted.  Not sure if they are real.  The spindles have numbers but they are not very legible.  The car spent most of its life in the South 1969-1971 Alabama,  New Orleans 1971 - 2009.  Its amazing how bad these parts can get even living in the Deep South there whole life.  Thanks again,  Jon 

[KurtS]

Those aren't castings, those are forgings. Very different process.

> When something is cast, the material is heated above its melting temperature and poured into a mold where it solidifies.
> When something is forged it is physically forced into a shape (in a die) while remaining in a solid state – although it is frequently heated.

[boomer632]

I referred to parting lines on those which I should clarify as well. Like crankshafts, thin parting line is indicative of a casting, wide parting line indicates a forging.