drum brake master cylinder date stamp format

[mtull]

I'm trying to understand how to read the assembly date on drum brake master cylinders.  I've seen mention of a 3 digit day of year followed by a single digit referencing the year. The first image is from a thread on this site and appears to have a 5 digit number: 12988?  The second image is from a master cylinder with AANF cast on the bottom and appears to also have a 5 digit number: 2968x?  The last digit looks like a '4'?

If I understand correctly, a 1969 10,000 day calendar defines 2968 as September 12, 1969 however that doesn't take into account the last digit?  I could also read it as the 296th day of 1968; October 22, 1968.

Any education help appreciated.
Thank you

[Cuda Cody]

Almost looks like a 1?  It was common to put the number of the shift that did the work.  For example, a number 1 or 2 would just indicate that it was the 1st or 2nd shift working that day that did the work on the part.

[mtull]

Almost looks like a 1

Could easily be a 1.  The last digit in the first image looks like an 8.  How many shifts per day?  Head scratcher for sure

Thank you for your input @Cuda Cody

[JH27N0B]

I studied master cylinders some years back and documented the info for Mopar master cylinders.  I never completely sorted out the '67 through 70 drum brake master cylinders.  They were used across almost all platforms at the time for drum brakes, unlike disc that had different master cylinders for different platforms.  And maybe due to how many they needed, they may actually have been built at multiple plants to supply the large demand and there were no doubt nuances between procedures at the different plants.
There are 3 different casting numbers and numbers stamped in them for internal use and for the date code are found in different locations.  The one you show is in the nose but I've seen numbers stamped in the side of the casting on other examples.
The date codes on the disc MCs were rather straightforward to figure out. Like 9 123 would be the 123rd day of '69.  But the system on some other master cylinders like these drums seem to be in a different format I don't completely follow.
I don't recall off hand on drum masters, but on disc there were also casting date codes cast into the body.  They used a removable plate in the mold so you see the outline of screw heads by those date codes.  Dan 6bblgt studied those and figured them out, offhand I think they were month and year. That doesn't tell you when it was manufactured, but at least tells when the casting was made, so it was typically not very long before the part was machined and assembled at the plant, which at the time was a Bendix plant as they made all the master cylinders for Chrysler.

[mtull]

They used a removable plate in the mold so you see the outline of screw

Thank you for you're post packed full of good info.  The removable plate detail was an interesting tidbit.  Regarding your statement: "I never completely sorted out the '67 through 70 drum brake master cylinders", did any of the one's you reviewed have a four digit date stamp (ddd y)? Thanks for your response!

[JH27N0B]

I'll have to look at some drum brake master cylinders I have at home, to see if they have the plate feature with the casting dates like I have seen on the disc brake MCs.  I have a couple drum brake master cylinders with the date code info stamped in the side, that seem to fit the format I see on disc brake ones.  The both started in 6's, so that brings a question was that '66 or '76. If '76 they would have been made as service parts. Those 2 are also E coated black so that brings another question to the mysteries with these.  Were all E coated, were just some, was it only for a brief time?
Noel Automotives YouTube channel recently featured some interesting videos documenting a survivor '70 Challenger R/T and the drum brake master cylinder on that car has its casting E coated black.
The disc brake master cylinders of that era, were black too, but they were clearly painted black.  Some Bendix MCs for other of the big 3 carmakers I've see were E coated, not painted.

[mtull]

I watched/enjoyed the video's he did on that car.   It's a sharp car IMO. I'm grateful for what he shared and wouldn't have complained if the video's were longer. 

Thank you @JH27N0B for helping me get my head around this topic.
 

[JH27N0B]

I looked at the ones I have.  2 I believe are NOS and have casting number 2225601.  Both E coated black.  One has what I believe is the date code and it's stamped 7 192 and the screwed in plate in the casting mold reads 146 in the casting.  The other is 6 342 and the number on the screwed in plate is 254.
The last one is rebuilt and has AANF as its casting number.  It has 346 stamped in nose and no numbers on screwed in casting plates on it.

[Gr8White]

Hey Mtull, this is a subject of interest to me, too. Like to know if your's were known originals or just mystery m/c's that you have there.

I've seen 2 drum m/c's stamped like the one in your first pic - looks like your's was stamped BT2998, which should be a 299th day of 1968 unit. I have one m/c here that is stamped (also on the nose/snout) BT3217 and, and I have seen one other that was stamped AT3253 on its snout. The AT and BT 'prefix' assigned as shifts? -or- plants? -or- internal #?.

Your second m/c looks like it reads 2968 and that the last 4 'seen' (some may also see) is just the textured surface appearing to only resemble a 4. So that it too looks like a (4 digit date stamp) 1968 unit, assembled 296th day.

JH27NOB has done some really great researching and helps out on plenty of Mopar m/c's questions, appreciate all he's doing. His 2 m/c's I would date as 7  192 is 192nd day of 1977 and the other 6  342 as 342nd day of 1976. The first digit should be the year. I am thinking these are from the 1970's and not the 1960's & I'll explain why below. From what I've learned and then using a common sense approach. His 346 dated AANF unit could be 346th day - the year is missing - the year may have never been stamped.

It looks like Bendix MOSTLY employed a four digit date code system for the 1" bore double-hump, (while some are found with only 3 digits.) Consider that Mopar's 10,000 day calendar may have only been widely used for tracking Mopar engines and transmissions. I'm doubting that Bendix had adopted/followed Mopar's unique (strange internal 1962-87) 10,000 day calendar. Whoever thought the 10,000 day calendar was involved must not have considered that, so some date combinations (like your 2698 & 2998) will produce a false 1969 & 1970 date - if using the 10,000 day calendar. There is little reasoning and little evidence for Bendix using the 10,000 day calendar.

Then 10 years after production began in Aug 1966 reinvolves falsely dating a 1966 vs 1976, 1967 vs a 1977 unit - 1968 vs 1978 - 1969 vs 1979 and lastly 1970 vs 1980.

Already mentioned is Bendix plants looked to only date stamp in the snout or the side, most side stamped units I've seen in the past were stamped on the engine side. Stamped in the snout units seem to be the last (4th) digit is the year, while side stamped units look that the first digit is the year.

I also have a m/c here that only has 3 digits in the snout - so the year must have been left off of/omitted from some snout stamped units occasionally. Having at the least the 3 digit days of year stamped was most important, important for issues like recalling a bad batch, and these 3 digit stamped units seem impossible to determine their specific built/assembled year. Consider that apparently not all units were date stamped to begin with.

Some snout stamped units were stamped with equal spacing, ex 1329 (132nd day of 1969) - others have some space between the 3rd and fourth digits, here as an ex. 132  9. The year is set slightly away from the days.

But side stamped units appear to differ however as an ex. 9  132. (1969 132nd day) In those the first digit represents the year with some space between the 1st and 2nd digit.

The 1967-69 units are 'easier' to decipher, its 1970 units are harder in that say an ex. 0120 date code could either have been the 12th day of 1970 -or- the 120th day of 1970 - one Bendix plant may have stamped the year with the first digit and other plant stamped year as the last/fourth digit.

Consider also that Bendix (from different plants in US & Canada) may have continued to make the drum double hump m/c up and until the early/mid 1980's, a 1977 dated AANF casting is the latest NOS unit I've seen.

My guess is the factory line units from Aug 1967-July, 1970 were mostly bare/natural, and starting in August of 1970, as the all new for 1971 drum m/c was being shipped to Chrysler in bare natural, some Bendix plants began the black paint/e-coating for their newest 'service' m/c's, (keeping all the 1967-70 cars on the road with a new replacement m/c) and the other Bendix plants did not e-coat or was just a random thing. That just would mean that a majority of black drum m/c's were probably made between Aug 70 through to the 1980's? Bendix would continue their contract to supply Chrysler all of their new, over the counter/NOS/dealer-ordered m/c's, as soon as production line and all 3 of the 1970 part numbers ended in July 1970.

There were lots of NOS Bendix drum m/c's that are black, it seems more likely that an all original 1967-70 Mopar with a black m/c is wearing an NOS/aftermarket (post 1970) and its original m/c was pulled/replaced sometime before the new owner took possession. It also makes sense that sometimes Bendix was supplying the prod line smaller 'batches' of black e-coated m/c's at anytime during 1967-70. Bendix was randomly coating the 1967-70 assy line power booster and drum m/c as combos in the black e-coating as it was, or so I think that's what I've seen and may be widely accepted.

NOS drum m/c units are either black (gold cap with bare clamp and bare bolt) (and some units their gold cap and clamp and bolt are also black e-coated) -or- they are simply a plain/bare casting with gold cap and bare clamp and bare bolt.

Bendix appears to have also supplied / sold to the aftermarket, exclusively, during the 1970's-80's (companies like Raybestos/Wagner) with new 1" bore drum units, purchased for a simple re-lable.

Once Bendix quit making the drum double hump, again maybe sometime in 1980's, that required AFTERMARKET companys like EIS, Raybestos, Wagner to begin to create their own unique castings, each having their own subtle differences over the original Bendix design. By now all the entire USA brake aftermarket sold out to China long ago. The Chinese are surely very found of their (Dorman/Raybestos brands) castings we started seeing at parts stores beginning in the 2000's. If it turns out the Chinese do at least make the world's best Mopar drum m/c then we're still good. Brand new Chinese m/c's are up to/priced at $100 each at some places.

To add how it looks like the Dorman TP59091 m/c rebuild kit from China is the ONLY kit that seems to be readily available anymore. New Chinese made kits to rebuild 20 years worth of Chinese made m/c's, what can you do!

I tried to use words like maybe, might, could, should, and also try to come to a reasonable conclusion - since I did not have access to any of the above info when it was happening, its all mostly a rehash of what others on the Mopar forums have shared in the past, happens to be most of what I learned about the old reliable 1" bore double hump.

Mopar assigned just one part number from 1967 to 1969. Kept things simple. In 1970 the confusion started when 2 more part numbers were added, Mopar should have just kept the 1967-69 part number for 1970, since all 1" bore castings will fit & function all 1967-70 A/B/C/E bodys.

One question concerns the AANF castings. Did the AANF make its first appearance starting in Aug 1969. The AANF 1" bore castings seems to be 'linked' only to 1970 C & E bodys. Did any 1967-69 A/B/C body cars have an AANF as original. The AANF castings also are seen on some 1971 disc brake m/c's - and are easily identified as such.

[Gr8White]

Here is a typical engine side date stamped double hump (5  141 - being 141th day of 1975) as well as a 1971 AANF casting disc m/c

[Gr8White]

Some units, like this one below, the date stamp in the nose/snout is sideways. That implies either different Bendix plants had their own way of doing it, or the same plant would change it up randomly throughout the year -or- maybe the day shift preferred one way over the night shift!??!

[JH27N0B]

Great research info there.
I wanted to point out a few things concerning the aftermarket.  I worked for Brake Parts Inc from 90-2005, they sold brake parts under the Raybestos and NAPA United names and even did Delco's replacement brake parts for their cars after they reached a certain age, that started late 90s if memory serves.
We had catalog researchers who studied the OEM parts listings for new brake parts part numbers.  When the found a new part number, a part would be ordered from a dealer, engineers would analyze it, and a new Brake Parts Inc part number assigned if it didn't turn out to already be an existing part. The part would be disassembled and we'd find what components were existing parts we made and what needed to be tooled to make.
A cost analysis would be made using demand forecast.  If the payback was short enough, we'd design the parts, and tool up to make.  If the cost analysis was not good, our purchasing department would source to add it to our line.  Typically from the OE source.
So some master cylinders like this drum brake master would have been tooled up and produced from the beginning.  Others like the one year only '70 E body disc were never made by any aftermarket brake company.  Purchased by all the aftermarket brake companies from Bendix until they stopped making them probably 1977 or 78 timeframe.
Our parts standards were to fit and function like OE, but weren't meant to be "restoration parts". Our master for the 1967-70 drum brake Mopars had a bale wire cap not the bolt on for example. Aftermarket companies fixturing for machining castings was different than Bendix, so all aftermarket Mopar MCs looked different than OE.
I remember a time in the 90s we had some issues with Asian suppliers and it was decided engineers had to do a first piece approval of any new Asian part.  Corvette MCs of that era were from a company in Australia called PBR.  For some reason we considered Australia to be Asia, and I had to approve the first PBR samples.  It was considered more trouble than worth to send the first piece back to the plant afterwards, so I was told to throw them away after approving.  They were sourced from PBR, so OEM.
I decided to "lunch box" them out the door instead of tossing in the trash.  They listed for around $300. I couldn't bear to throw a valuable brand new part in the trash even though I had no use for it and never would.
But I'm not a Vette guy, how do I sell them?
I had 3 different PBR Vette MCs on a shelf in my garage gathering dust for over 5 years.
Then in 2001 I signed up for eBay and started listing some of my clutter including those parts.
The Vette MCs all sold, I think I got over $100 each for them!
My pack rat frugal mentality paid off! eBay sure was a game changer for me when I started using it. Too bad it sucks now!
I found records of when engineers had analyzed a number of Mopar Muscle era MCs.
We kept samples, but I was told they did a big housecleaning sometime a year or 2 before I was hired and obsolete samples got scrapped.
I still shed a tear thinking about how there was a 70 E body disc and 70-71 hemi disc MC that we'd analyzed, and on the sample shelves for almost 20 years, but thrown away and wasted!
But I copied all those analyses sheets and that is how I learned all the correct casting numbers for 60s and 70s Mopars, and shared it with everyone.

[Gr8White]

This NOS engine side stamped drum m/c is slightly different than the first one I posted above. Made in Canada is seen stamped into the first line. Underneath the Made in Canada though is the same 'E5665' internal Bendix code as the one above.

My guess is its dated (6  142) 142nd day of 1976, someone else may have a different date in mind, I'd be interested in finding the how's and why's it isn't deciphered as that date. If it is in fact the 142nd day of 1966 that was May 22, 1966. That seems too early in the year to have been ready for the new 1967 models that began in Aug, 1966. Its roughly 90 days before the first car of 1967 would need it. And it could be that Bendix didn't start ink stamping Made in Canada on the side until the 1970's, a clue that its a 1976 made unit, not a 1966. Bendix probably had quit making these by 1986, so then it rules that date out using this reasoning.

[Gr8White]

Here is a pic I had saved of one owner's drum m/c - believe they stated it was an AANF casting m/c and can see the date (053  code stamped in the old snout. Seen in pic is how there is a significant amount of space between the 3rd and fourth digit. Again that looks to be done to quickly differentiate the year from the days. Most likely was assembled the 53rd day of either 1968 -or- 1978. If its a 1968 built unit, then, my question above of if the AANF casting was created for use on any 1967-69 cars would have at least this one as some 'proof.' We see the 'Feb 68' in ink is how most all of us would & should decipher that date code as the build date.

If its a 1978 unit, then it just is, anybody that knows more could present here or in some future discussion held in some smoky garage.