Can you tell a repop from an original 67 master cylinder?

[Joe R.]

Re: Can you tell a repop from an original 67 master cylinder?

Thanks, my 68 has the same cap as the 67.

Hi Jack:

I could be mistaken, but I thought the 68 cap had different text, with a reference to an SAE spec for the brake fluid. The 67 cap does not mention SAE.

[Joe L.]

Re: Can you tell a repop from an original 67 master cylinder?

I built patterns for a lot of the master cylinders from 1963 on. They were for Delco Moraine. They were cast in Coldwater Mi. at Midwest Foundry which was a gray Iron foundry. I don't recall any master cylinders made with anything but gray iron. no reason. Calipers heads blocks were all gray iron. In fact ductile iron as it was fairly new alloy & had to be licensed by a British co. was not used on cars till later & only because they were trying to save weight. Malleable iron/ductile was only used because of its tensile strength for flexing ability not strength. Rear ends were made of malleable iron because they needed to flex a bit at Albion Mallable in Albion Mi. for Dana/GM in the day
KEN

Ken----

The 1967 to at least 1973 Corvette master cylinders were cast at GM's Danville, IL foundry (actually, it was in Tilton, IL but that's near Danville and the foundry was known as the Danville foundry). If one examines one of these master cylinders one will almost always find a "D" on the casting which is the foundry mark used by the Danville foundry. Also present will be the "wagon wheel" symbol identifying GM's in-house Central Foundry Division. Of GM's 6 in-house cast iron foundries of the day only Danville and Tonawanda commonly used casting marks to identify the foundry. In any event, Danville was a malleable/ductile iron foundry although they may also have poured some nodular iron. As far as I know, Danville did not pour any gray iron, at all.

1965-72 Corvette brake calipers were also manufactured of malleable/ductile iron. This material was known as "Armasteel". In fact, L1967-72 front caliper outer halves usually have the word "Armasteel" embossed on them. Most, if not all, of these calipers will be found with Danville's "D" casting mark.

In about 1973, the Corvette calipers were changed to gray iron. I believe that these were cast by some outside foundry. None will be found with a "D" casting mark.

I agree with you that the surface finish of a casting is primarily due to the sand used in the casting process. However, the sand used may have some relationship to the type of material cast. In any event, for whatever reason, Danville must have used a finer grade sand than is commonly used. As I mentioned previously, if you compare a Danville master cylinder to a non Danville, you will note that the surface finish on the non Danville is rougher. Also, if you compare the surface finish on 65-72 caliper halves with the 73-82, you will note a considerable difference in surface finish. The 73-82 are MUCH rougher. In addition, if you compare the surface finish on any Danville malleable/ductile iron casting, brake related or otherwise, you will note a much smoother finish than found on gray iron castings from Saginaw, Tonawanda, and Defiance.

[Gerard F.]

Re: Can you tell a repop from an original 67 master cylinder?

Hi Jack:

I could be mistaken, but I thought the 68 cap had different text, with a reference to an SAE spec for the brake fluid. The 67 cap does not mention SAE.

Cheers Joe,

According to the 68-69 Judging Guide, the "Use Delco SAE J 1703 Brake Fluid" didn't come into effect until later in 69. The 68 (and early 69) Master Cylinder cap had the "Use Delco Brake Fluid Only" same as the 67.

Actually the 67 was supposed to be the 68, and they share a lot of identical parts.

I think Jack is correct with his 67 cap on a 68.

[Kenneth B.]

Re: Can you tell a repop from an original 67 master cylinder?

Sorry Joe. I stand corrected. Were they made for Delco Morine. Are you saying that all master cylinder castings for Corvettes were made at the Danville Foundry.A lot of the patterns we made were the two chamber ones which I assumed were for Corvettes that I made for Midwest Fdy a gray iron fdy. Why would they need to be made from DI?
KEN

[Joe L.]

Re: Can you tell a repop from an original 67 master cylinder?

Sorry Joe. I stand corrected. Were they made for Delco Morine. Are you saying that all master cylinder castings for Corvettes were made at the Danville Foundry.A lot of the patterns we made were the two chamber ones which I assumed were for Corvettes that I made for Midwest Fdy a gray iron fdy. Why would they need to be made from DI?
KEN

Ken-----


Yes, they were made for Delco-Moraine---cast at Danville and shipped to Delco-Moraine in Dayton, OH for machining and assembly.

I don't know that all Corvette master cylinders were cast at Danville. However, I believe that all 67-72 were, both '509' and '346'. After 1972 there may have been a change; I don't know, for sure. Some pre-1967 masters were cast at Danville, too. The 65-66 power brake m/c is one of them. I believe there are others, too. It's easy to tell. If they have a "D" casting mark, usually accompanied by a "wagon wheel" symbol, then they were cast at Danville.

I don't think these master cylinders needed to be cast from malleable/ductile iron but that's what Danville normally produced. I believe that was GM's only malleable/ductile iron foundry although one of the Saginaw foundries (not Saginaw Gray Iron, though) may also have poured some. Obviously, malleable/ductile iron is a better and stronger material than gray iron, so whether the master cylinders needed to be cast from it or not, those that are will be better pieces than those that are not.

As I mentioned, the 65-72 brake calipers were definitely cast of malleable/ductile iron and at Danville. Subsequently, the calipers were cast of gray iron, so this pretty much demonstrates that at least the calipers did not need to be cast of malleable/ductile iron. However, and importantly, the design of the patterns (and casting numbers) was changed when gray iron was used. The calipers were made thicker in some areas, presumably because the gray iron was not as strong as malleable/ductile iron.

[Joe R.]

Re: Can you tell a repop from an original 67 master cylinder?

Hi Jerry:

How about posting a good photo of the "recessed area" in your reproduction MC? I'm curious whether it differs from the original that I posted a photo of. As I recall, the reproductions are slightly different in this area.

[Gerard F.]

Re: Can you tell a repop from an original 67 master cylinder?

Hi Jerry:

How about posting a good photo of the "recessed area" in your reproduction MC? I'm curious whether it differs from the original that I posted a photo of. As I recall, the reproductions are slightly different in this area.

Joe,

Here's a shot from that archived post:




Not sure I can tell the difference in the casting in not having them side by side. But you can see the difference in the SS bleeders and bales.

Here's yours:

[Joe R.]

Re: Can you tell a repop from an original 67 master cylinder?

Hi Jerry:

I found this photo that I took at Carlisle a couple years ago, right after the reproductions came out. One of these is a repro, and the other is a restored original.

I *think* the repro is the one in front, but I'm not positive. The difference in the recessed area is fairly evident in this photo, but I agree that you really need to have two units side-by-side to see the difference.

[Tom M.]

Re: Can you tell a repop from an original 67 master cylinder?

Joe,


I think the repo is on the top, is that what you meant?

[Joe R.]

Re: Can you tell a repop from an original 67 master cylinder?

Joe,


I think the repo is on the top, is that what you meant?

Hi Tom:

I think the repro is the one on the bottom (in the foreground), but my notes from the day I took that photo have been lost, so I'm not positive. The intent of the photo, though, was to compare an original and a repro.

I have two original units, and both of them have a wider recessed area like the unit on the top in the comparison photo. Earlier in this thread I posted a photo of one of my original units, with the recessed area circled. If you compare that known-original unit to the two in the comparison photo, it looks like the one on the top.

As I noted earlier, it is possible that both styles appeared in original units. All I know is that the two originals I have look like the unit on the top in the comparison photo. I'm hoping that others with known-original units will comment on the photos.

[Gerard F.]

Re: Can you tell a repop from an original 67 master cylinder?

Joe,

I think the one on the top of your picture is the repro, like Tom.

The reason I say this is for another difference which looks like my known repro (picture above). My repro has a little more pronounced bulge in the body just aft of the forward bleeder. If you compare my picture above, and the one at the top in your picture, you will see the same bulge, unlike the one in the bottom of your picture.

Maybe we are splitting hairs on the differences. I'm sure that there was more than one mold for these master cylinders, and lots of other differences between originals.

But it's fun splitting hairs.

[Rick S.]

Re: Can you tell a repop from an original 67 master cylinder?

Hi Jack:

I mentioned the cap fonts in an earlier email, but a photo helps to clarify the differences. Since the TDB won't let me upload the same photo twice, see the photo in my earlier post in the thread at:

https://www.forums.ncrs.org/showthre...60881&uid=2785

In particular, compare the "W" and the "D" characters.

Joe,
I faced the same problem Chris has with the replacing of an incorrect master cylinder. I bought one from Muskegon Brake a few years back and they also provided a cap which appeared to be original. I had the cap re-plated and was wondering what you thought of its accuracy. Not the best photo but I am willing to take it off to provide a better photo, if needed.
Rick

[Chris E.]

Re: Can you tell a repop from an original 67 master cylinder?

Wow, this thread sure went a lot farther than I thought it was going to.

So, here are the summary points, if I'm reading everything right.

1. The repops are REALLY close to the originals, and some judges even at regional or nationals will not be able to tell the difference.

2. Put the repop on and be happy.

Am I right?

[Gerard F.]

Re: Can you tell a repop from an original 67 master cylinder?

Joe,
I faced the same problem Chris has with the replacing of an incorrect master cylinder. I bought one from Muskegon Brake a few years back and they also provided a cap which appeared to be original. I had the cap re-plated and was wondering what you thought of its accuracy. Not the best photo but I am willing to take it off to provide a better photo, if needed.
Rick

Rick,

Not sure about the lettering question, but here's a picture of what I believe is an original 67 master cylinder cap just coming out of the dichromate tank:

The one on the left, I believe is the original and I did the plating for another member here. The one on the right is a 69 or later with the SAE BS.

Don't know if you can see the letters, but note the crisp-ness of the pressings of the bosses that hold the bales in place. They seem to look like yours, especially in comparison to the later one.

And Chris,

Seems like you have brought out the anality of some members here. We are just having fun.

But don't get too cocky, it is going to depend upon the judge who looks at your master cylinder.

[Rick S.]

Re: Can you tell a repop from an original 67 master cylinder?

Jerry,
Thanks for your valued opinion. I think it is the real deal and was looking for confirmation. I am not going to change it as I feel it is "good enough for government work". Being a life long government employee, I think I can say it with tongue in cheek.

Regards,
Rick