Hi
On AC Delco PWR Brake Master Cylinder there is a stamp of OD2, OD3, OD4, OD5, OD6.
Does someone know the deference between OD3 to OD4?
I have PWR Brake Master Cylinder# 5468309, OD4 (72 conv')
Thanks, Avner

 

This is a casting mark isn't, not a stamp. I believe what you are looking at is a logo and not a 0. I need to double check but I recall that this pertains to the casting. The letter is the shift and the number is the mold used. If it is dated, that will be julian date stamped on the machined surface of the front outlet.

 

Hi RPOL68
You right it's kind of a logo (0 with X inside),
What you mean by: The letter is the shift and the number is the mold used.
My MC is dated stamp also 260

 

These are foundry marking. There were several molds these were cast from and there were several work shifts that made these. If a problem came up the foundry would want to know exactly when and which mold made the part in question. There is not a functional difference based on the foundry's casting mark.

I'd have to recheck my references but I think the year came before the Julian date on these. In you case your M/C was assembled on the 60th day (March 1) of 1972. The casting was made during "D" shift using mold number 4.

 

OK, the O with the * in the middle is the Central Foundry logo. There were 11 patterns used to cast master cylinders. They are identified by the D1 through D11 casting marks.

Julian dates can have the year as the first or the last digit. It is speculated that the day shift had the year perseed the date and the night shift had the year folling the date. So in your case it could also be Jan 26 1970.

 

I saw that some say that the date is the number of the days from
Jan/1 so 260 is 3 week of June with no year at all.
My body build date on the trim tag is K09.

 

That is how the Julian date works. Actually, they have a formula that gives a individual number to every day in history. But what we are looking at here is the yearly julian dates. 260 is September 17th, but that wouldn't indicate the year.

In the case of the stampings on the master cylinders the year is indicated by either the 1st or last digit. These were stamped with either 3 or 4 digits.

Yours is 03/01/72 or 02/26/70.

K06 would be a June 6th assembly date for your car. So 3 months between the M/C being built, shipped, stocked and put on the car is accepted as typical in the assembly process. Sounds like you have the original master cylinder. Certainly worth keeping and rebuilding if the time comes.

 

Thanks RPOL68 for the information
But I never saw a date code with 4 digits,
I look at ebay for a long time on the M/C ads.
Avner