Duke, forgot to mention. Bob Jorjorian emailed, said the other number that Harry posted, 3813859, was for a 1959 Chevy Biscayne taxi, so don't ad that one to your list of Corvette drums.
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Re: Correct for 63-65 fronts
Just to add more confusion to the discussion, what is this?
Harry -
Re: Correct for 63-65 fronts
Same part number, same basic front drum, but with a few minor changes that called for a new casting number. Probably released a few years after the original casting. I've seen several of these over the years. Actually more common than the original casting number.Comment
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Re: Correct for 63-65 fronts
A 166 base drum with a casting number of 672 is exactly what I speculated on in a previous post. The web is part of the casting and the thinner web of the base drum would mean a different casting number. I guessed it was probably either 670 or 672 - in sequence with the 671 metallic brake drum casting.
DukeComment
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Re: Correct for 63-65 fronts
I'm stil thinking all the original 63 drums are cast 671. It was a two piece drum at that time and later, when it was mfg'd as a ome piece, the casting number changed. The 672 that's currently listed on ebay clearly shows the later design web with NO holes between the studs. The correct original design would have had the 5 holes between studs.
We need input on this so I think I'll start a new thread.
MichaelComment
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Re: Correct for 63-65 fronts
Are you saying this is NOT a composite drum i.e. the stamped steel web was not placed into the mold prior to the iron being pored and that there was a later "one piece casting" where the web is molded as part of the pour?
It doesn't make sense that drums with difference web thicknesses would have the same casting number.
Here we have a drum that claims to be from box marked with the base brake drum number ...166 with a ...672 casting number, both of which are sequential with the J-65 drum and casting numbers although "reversed".
Makes sense to me!
DukeComment
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Re: Correct for 63-65 fronts
We now have several known originals with the 671 casting number, both std and met. If I remember correctly, your red 63 also has the 671's and you know for certain that the drums are correct original. It's definitely beginning to point toward the fact that all original 63-64 drums (not Z06, obviously) were cast with this number. I believe the ring was the numbered part of the assembly and the web was used selectively before casting, as req'd for std/met.
I've never seen a 671 without the second set of five holes between the studs but I've seen many 672's that way. There were some pretty obvious changes that took place for the later casting but I don't have info as far as details.
I'm not exactly sure of the process so I can't tell you how or when the web was added.Comment
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Re: Correct for 63-65 fronts
You're ignoring the 672 casting in the 166 box on ebay.
I'm in no way convinced that both metallic and base drums were 672 castings - doesn't make any sense unless an engineering decision was made to use the thick web drums for all finished drums - both base and J-65, but didn't update the AMA spec data.
DukeComment
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Re: Correct for 63-65 fronts
No, actually I'm not ignoring it at all. It's a drum made for standard lining some time after a change was made to the ring. Note that it has only the five stud holes and no second set of five holes between. The 166 is the part number for a completed assembly and that particular assembly was the std drum. I'm betting there was a 672 for met available a few years later also, but with the correct original 3830167 part number.
I was going to go back in all of our email from last year to find out what the casting number was on your 63 drums but it's a lot easier to ask. What is it?
We have input from owners of several original cars now that do not have met but do have the 671 casting number.Comment
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Re: Correct for 63-65 fronts
My fronts are 671s and it's J-65.
Unless a '63 is an original owner car, or the current owner has production documentation, there is no reliable way to ID a J-65 car. If the shoes were replaced in service with conventional linings, which most have been, then the major evidence or J-65 is gone.
What's left is brake spring color, but the paint is probably gone.
DukeComment
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Re: Correct for 63-65 fronts
That means we have at least one of each so far. Harry Sadlocks 63 car has paperwork and is std lining. His front drums are 671's.
Your car is met and you have 671's.
It's very common to see a changed casting number when some change occurs to the part, but in many cases, the actual part number may stay the same. I believe this is exactly what happened to the 671 drum. They still retained the 3830166 part number even tho the casting number went to 672. I'm going to be very surprised if this isn't the exact way this happened. So far, we have no responses with 672 drums on any cars at all. Only 672's seem to be new in boxes, not originals on cars.Comment
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Re: Correct for 63-65 fronts
Duke-----
As far as I know, J-65 and standard brakes used the same casting for the drums. I believe that the only difference was in the surface finish of the finished brake drum.In Appreciation of John HinckleyComment
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Re: Correct for 63-65 fronts
There also was a difference in the actual drum web thickness between std and met lining drums. The standard drum web was .109-.119 and the web on a drum for metallic brakes was .125-.135".Comment
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Re: Correct for 63-65 fronts
All of those drums were centrifugally cast. Whatever web was required for the finished assembly was placed in the prepared lower half of the mold (which held the periphery of the web up about 1/4" off the floor of the mold), the upper half of the mold was added and clamped in place, the iron was poured, and the mold was spun to evenly distribute the iron as it cooled, in a continuous process. The sprues were on the inboard flange of the drum surface, and disappeared during finish machining.Comment
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Re: Correct for 63-65 fronts
Thanks John. Interesting stuff. I was sure the web and ring were separate pieces, just never knew the method used to attach the two together. Hopefully, now, everyone will understand why/how the thin and thick web of both styles of drums can have the same casting number on the outer ring. I was running out of ways to explain it.
I may borrow your explanation and repost in the latest drum discussion, if you don't mind. Thanks again,
MichaelComment
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