1966 427 power steering pump pulley

[Bill C.]

Hello,
I have two what I believe are original GM supplied pulleys for 1966 427 power steering pump applications. They are both casting # 3878245 DK . Both have been on my shelf a long time, I just cleaned them both up and see a difference in the castings and the way each was machined.

The one in the LH pic is representative of what I am accustomed to seeing, it has a pronounced raised cast area machined finished on the OD of the face, and the rear face. Also a raised machined area under where the retaining nut would seat.

The one in the RH pic has a flush face, without the raised area in either location on its face although it does have it on the rear, and its more pronounced, deeper if you will. The face of this one appears to be hit lightly wit a disk grinder in an attempt to give it a finished look I assume.

Dimensionally both are identical as measured on a surface plate between the rim and hub stop.

Could this be attributed to mold shift when cast?

Anyone seen one like this before?

Curiosity has gotten the best of me!

Thanks, Bill Caldwell

[Bill C.]

Re: 1966 427 power steering pump pulley

Here are pics of the back.

Also, I know the JG indicated this pulley be natural. Have any originals been noted with any paint at all?

[Ronald L.]

Re: 1966 427 power steering pump pulley

Bill,

The one has been rough machined where the other not, that is on the front surface. Why that was...I'd ask... was it a early part? Can you see that style on un molested early cars and then the other style on later cars?

I don't see anything that shows the casting is significantly different between them, only the balance holes show it was a little lopsided, but probably normal.

[Bill C.]

Re: 1966 427 power steering pump pulley

Ron,
Thanks for responding, thats what I was thinking, that it was an early original.
Was just interested in hearing if anyone else had seen one of these in this form.

Any thoughts on finish variations?

Bill