Holley dates vs Engine assy dates
 

For Holley carbs dated in 1969 - 1970 how did the syntax identify the specific weeks? For example, an 054 date would indicate 1970, May, 4th week and it is my understanding that week one would be the specific week where May 1st occurred. So, if May 1st and 2nd was a Friday and Saturday a date of 051 could make the 1st week all of 1 or 2 days.

What say you?

Good question,I've always wondered what exactly defined it as a week to them,(Mon-Sat?),as well as to other manufacturers.

Exactly!

We holley carbs dated 054 on Yenko Deuce Novas that have build weeks of 05D which aligns, and with engine assy dates of 0520 which on the surface would appear to be a conflict. However, the first technical 'week' for May in 1970 is just 2 days; Friday 5/1 and Saturday 5/2. So, that means 05/20 is Wednesday of week 4, which does align. Given the 1/2 year issue for 1970 we find that the component dates are very tight!

The same question applies to Fisher Body and other manufacturers that used week dates. Some manufacturers were more disciplined in the date applied, some left it more to the operators to implement. Fisher was in the latter group, fwiw. :)

Thanks Kurt, it certainly makes tracking down 'Dated Components' a bit more difficult - a nod to Jeff Dotterer there as well, IYKYK!!

Yeah, you’ve got the right idea on how Holley dated those. The first number is the year and the next two are the week of that year. So an 054 would be 1970, 54th week — which really just means early ’71 production. The “week one” thing wasn’t always a full week either; sometimes it started mid-week depending on how their production calendar lined up. Short weeks like that were actually pretty common.

Freddy there wasn't a year with 54 weeks in them.
That deciphers as:
0=Last digit of model year,in this case 1970.
5=Month,May
4=Week of month,4th week