Author Topic: 1966 GT350 rear drum outter edge machined - Why?  (Read 760 times)

6s1640

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1966 GT350 rear drum outter edge machined - Why?
« on: November 09, 2022, 11:13:18 PM »
Hi all,

Shelby Parts and Restoration, when restoring the rear drums, puts a fresh machining on the outer edge.  Does anyone know why they are machined to begin with?  I am assuming just to round out the casting, but just this edge.  What's wrong with the rough casting?  The rest of the outside is rough.  Any ideas?  Maybe to get a better balance and less counter weight?  See attached image.

Thanks

Cory
« Last Edit: November 09, 2022, 11:15:50 PM by 6s1640 »

Bob Gaines

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Re: 1966 GT350 rear drum outter edge machined - Why?
« Reply #1 on: November 09, 2022, 11:38:28 PM »
Hi all,

Shelby Parts and Restoration, when restoring the rear drums, puts a fresh machining on the outer edge.  Does anyone know why they are machined to begin with?  I am assuming just to round out the casting, but just this edge.  What's wrong with the rough casting?  The rest of the outside is rough.  Any ideas?  Maybe to get a better balance and less counter weight?  See attached image.

Thanks

Cory
Not all of the 2 1/2 drums came with the edge machined originally. Some came with a rough cast outer edge. I don't know why one comes machined and the other not. As Special Ed is fond of saying " that's just the way it is "
« Last Edit: November 10, 2022, 05:22:51 PM by Bob Gaines »
Bob Gaines,Shelby Enthusiast, Shelby Collector , Shelby Concours judge SAAC,MCA,Mid America Shelby

hertz1966

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Re: 1966 GT350 rear drum outter edge machined - Why?
« Reply #2 on: November 10, 2022, 12:36:46 PM »
Hello,

Two possible theory's on why the outer edge of the drum is machined.

1.  During the casting process there could have been excess cast material left on the drum, and to clean off the excess material it would be simple operation to face off the outer edge.  Later on maybe Ford repaired or changed the mold casting design to repair the defect and eliminate the secondary operation.  Maybe different casting plants had different cast molds.
2.   There could have been a secondary operation where they needed to grab the drum from the outside diameter and do a turning operation.  I think this is unlikely, you would chuck up the part from the center diameter of the drum and then perform the turning operation to clean up  the inside diameter.  I cant think of a reason why you would need to mount the drum from the outside diameter and perform a turning operation.

Just a theory.

Thanks,

Tim

s2ms

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Re: 1966 GT350 rear drum outter edge machined - Why?
« Reply #3 on: November 10, 2022, 02:57:10 PM »
My original drum edges are not machined.
Dave - 6S1757

J_Speegle

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Re: 1966 GT350 rear drum outter edge machined - Why?
« Reply #4 on: November 10, 2022, 03:20:48 PM »
Would be helpful, if we're going to look into this, that we get people to include the casting dates from the drums. Just a thought and a confirmation if they are original or replacements  :) if we want to go that far
« Last Edit: November 10, 2022, 05:47:09 PM by J_Speegle »
Jeff Speegle- Mustang & Shelby detail collector, ConcoursMustang.com mentor :) and Judge

s2ms

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Re: 1966 GT350 rear drum outter edge machined - Why?
« Reply #5 on: November 10, 2022, 06:57:55 PM »
Good idea Jeff...

My originals are dated 2-1-66 and 2-3-66, both are male.... ;)
Dave - 6S1757

6s1640

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Re: 1966 GT350 rear drum outter edge machined - Why?
« Reply #6 on: November 11, 2022, 11:46:08 PM »
Hi Hertz1966,

Your (1) is what I was thinking, the outer edge was cleaned up due to casting flaws.

(1)  During the casting process there could have been excess cast material left on the drum, and to clean off the excess material it would be simple operation to face off the outer edge.  Later on maybe Ford repaired or changed the mold casting design to repair the defect and eliminate the secondary operation.  Maybe different casting plants had different cast molds.

Hi Dave,

You had me going there with "both are male" for a day.  You mean no nubs.

Cory


s2ms

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Re: 1966 GT350 rear drum outter edge machined - Why?
« Reply #7 on: November 12, 2022, 04:40:31 PM »
Hi Cory,

Yes, no nubs. Was thinking of the "other" term used to describe those....

Dave
Dave - 6S1757