Date decipher on cast iron thermostat housing

[Garry B.]

I have the correct part number on my thermostat housing, but can't figure out the date of B3. Can someone decipher this for my '64 327/300 engine? Thanks.
Garry Barnes
#18531

[Mike E.]

Re: Date decipher on cast iron thermostat housing

Garry,
Are you sure that is a date code? I thought it was a mold number.

[Garry B.]

Re: Date decipher on cast iron thermostat housing

Mike, I have no idea. I thought it was a date code, but I have found three of them for sale on line and they all start with a B and end with a single digit. You may be correct. Anyone else? I did notice in the JM that there is no mention of a date code or how to read one. Thanks Mike.

[Bob R.]

Re: Date decipher on cast iron thermostat housing

I think Mike is correct it is a mold number

[David B.]

Re: Date decipher on cast iron thermostat housing

It could be a mold # but would not be too surprised if B3 is a date. From a 1975 Chevrolet Product Identification Manual " Delco uses a letter and number code to identify the manufacturing date (of it's thermostat) for example, a thermostat with a date code of J4 would have been manufactured during September 1974." While the housing may not be Delco it's close usage relationship suggests a possible similar manufacturing system.

[Garry B.]

Re: Date decipher on cast iron thermostat housing

Dave, thanks for your comments, but I have now found five of these things for sale on line and they all start with a B and have a single number following between 1 and 4. The application for this part is for C2's and your Delco publication is in 1975 which may or may not apply to parts made ten years or more prior. My car is pretty bone stock original and the patina on my thermostat is spot on with the rest of the intake and other cast iron parts, so I don't think it has been replaced. If the B is the mould designation, could the 3 (and other numbers) indicate the third mould of B?

[Garry B.]

Re: Date decipher on cast iron thermostat housing

Checking the archives I found comments back in 2004 from two of our esteemed members that I believe may answer the question as best as can be expected. Here's the first one from Jack Humphrey:

The 'B x' emboss is thought to indicate the specific cavity on a carousel mold the part was poured in for defect traceability (carousel 'B', mold cavity 'x')....

[Garry B.]

Re: Date decipher on cast iron thermostat housing

Here is the second one from Joe Lucia:

GM #3827369 is correct for your 1966 application if you have an L-79 (or, if you have an L-36 with K-19) . This housing was used for quite a few other applications, too. In some cases it also replaced, for SERVICE, some earlier housing part numbers.

The "B3" is some sort of casting code, perhaps a mold number. I don't know for sure, though.

[Kenneth B.]

Re: Date decipher on cast iron thermostat housing

Its NOT normal to have a letter by the pattern? impression #. Most of the time they are stand alone #'S on the pattern plate. If there were 6 patterns on a plate they numbered them 1-6. Also would not think it is the foundry trade mark.

[Ronald L.]

Re: Date decipher on cast iron thermostat housing

A picture is worth 1000 words...

[Garry B.]

Re: Date decipher on cast iron thermostat housing

[Ronald L.]

Re: Date decipher on cast iron thermostat housing

And the underside?

Any dots dimples a clock pointer and dots?

[Garry B.]

Re: Date decipher on cast iron thermostat housing

Have never had it off, so don't know what's on the underside. No other dimples, clock pointer or dots visible. Having looked at others, I see no signs of any of these things on them either.

[Kenneth B.]

Re: Date decipher on cast iron thermostat housing

After looking at the picture I am sure that the stamped B 3 is the B is the foundry trademark & the 3 if the pattern #.

[Joe L.]

Re: Date decipher on cast iron thermostat housing

After looking at the picture I am sure that the stamped B 3 is the B is the foundry trademark & the 3 if the pattern #.

Kenneth------


I think so, too. I don't think these housings were cast at a GM foundry. I think they were out-sourced to some independent foundry. The "GM" and "3827369" were part of the GM specifications for the part. The drawing probably also required a manufacturer's ID mark and that's likely what the "B" is. As many have opined, the numeral following the letter is very likely a pattern number emplaced by the foundry for their quality control purposes. This part is a sand casting and a pattern is used to make the sand mold.