BB 3899621 Bellhousing Casting Date Help

[Dereck S.]

I came across an original GM 3899621 big block bellhousing. I didn't think early 67 bellhousing may have had a 1966 casting date code. Please review the attached pic and indicate if this has a 66 casting date. There appears to be two dots and a "66" in the casting mark. Any help interpreting this casting mark would be appreciated.
thanks
Dereck

[Joe L.]

Re: BB 3899621 Bellhousing Casting Date Help

I came across an original GM 3899621 big block bellhousing. I didn't think early 67 bellhousing may have had a 1966 casting date code. Please review the attached pic and indicate if this has a 66 casting date. There appears to be two dots and a "66" in the casting mark. Any help interpreting this casting mark would be appreciated.
thanks
Dereck

Dereck------

Early 1967 bellhousings were definitely manufactured in 1966. Aluminum castings usually do not include a year in the casting date. The number in one half of the circle indicates the month of the casting. The dots in the other half indicate the week of the month. In your case, the digits in half of the casting are an unusual exception in that both the dots and digits appear in one half of the circle and and nothing appears in the other half of the circle. What I expect occurred was some kind of error in which two "6" characters appeared in the circle half instead of one "6" and both were somehow displaced to the same half of the circle as the week-indicating dots. The way the characters appear is additionally unusual. In any event, I expect that what this represents is the second week (i.e. 2 dots) of June (i.e. 6). The other possibility is that this is some sort of non-standard date coding in which the two digits does indicate 1966. In that case, I have no idea what the dots represent

[Dereck S.]

Re: BB 3899621 Bellhousing Casting Date Help

Joe
Makes sense. It's likely some sort unusual error.
thanks