I have read / been told the cars' pad assy date should be no more than 2 weeks after the engine casting date. Ive also read the VIN should be no more than 8 weeks after that.

Ive seen dates all over the map on cars and as reported on cars.

I also understand that NCRS allows casting dates up to 6 months before the VIN assy date.

Why the discrepancy? It would seem the 10 weeks is kinda far away from the 24 weeks (or 6 month) rule.

I was told once that early cars (56-62) had a tighter time frame. Any clarity on this out there? Is it about model years?

 

Well...NCRS is the definitive source on interruption and guidance of casting dates, assembly date codes and date stamps. NCRS wrote the book on originality and factory production standards. No one does it better cause no one else does it so its publications should serve as your source of guidance. Having said that...they are not perfect but the methods used are based on extensive observation, study and documentation.

But I'm unfamiliar with a VIN assembly date. What does that mean to you? You may mean the body assembly date that is derived from the trim tag and indeed NCRS does provide a six month guideline.

At the same time, I believe you're confusing yourself. There are many dates and many subassemblies such as engine assembly. This is different than body assembly and engine assembly precedes body assembly. Engines were built in another state (like Detroit) while bodies were assembled generally in St Louis.

 

Thanks, I guess. (?) I hate to sound rude, but I don't see the relevance of the 3 paragraphs of answer above other than to nitpick a slang term and state random factoids.

Excuse me for saying VIN assy date instead of build date according to VIN. Whats the difference between that and the trim tag build date, 1 day?

I know who NCRS is and what a source they are. I'm not sure the lecture on the expression on the VIN date was necessary, but I suppose if you think correcting it to say body assembly date is productive, whatever. I already asked about the 6 month NCRS guideline, so again Im not sure what was productive about that reiteration. Again, the final paragraph is another exercise in trying to appear to offer some sort of information, I suppose. I'm pretty sure I'm not confusing myself, but thanks for the suggestion.

I'll try one more time. Cliff notes version... NCRS says 6 months is OK, but it seems the vast majority of time frames between casting dates and "body assembly dates" (happy?) is closer to less than 10 weeks. I even took a sample of about 20 blocks to see for myself and found times frames of usually 3 weeks or so, with no more than 13 in one case. Anyone familiar as to why NCRS goes to 6 months, and if there are many examples of time frames closer to 6 months?

UPDATE- I got some helpful observations in the C1/2 section, mainly regarding the fact that blocks were often used in a first in, last out fashion, mixing the dates a bit. No further discussion needed here.

 

Your observations are on target. The majority of production Corvettes components do have a tighter assembly date time frame to the body build date as you alluded to in your previous post.

I believe NCRS includes the 6 mos time frame to include those Corvettes with the rarely seen options that do indeed have components that are not typically seen with closely dated componentry, such as ZL-1, L-88 & LS-6 big blocks, and probably the LT-1's optioned as ZR1's. Alot of these cars components are batch built and time frames extend beyond the norm.

 

Remember that there was a strike or strikes in 69 and then in 71

My 1971 has a pad date of V019 August 19th. block cast 08-14

Car was assembeled 12-01-70

I beleive in 1971 there wre not cars built in either September or October.

At the same time GM is a company like any other. And I can tell you there is the public perception of what goes on day to day and then there is reality.


David

 

vettebuyer, I have recently done a lot of reserch around 1) engine casting dates, 2) engine build dates 3) body assembly dates and 4) "birthdays". The simple answer for these 4 disparate dates is that NCRS rules require that the engine casting date comes first, the engine build date is after the casting date (obviously) and the body assembly date can be no more than 6 months after the casting date, and other dated components in order for them to provide maximum jugding credit. The purpose is to give lattitude for special options, disruptions in supplies, sloppy inventory management, and generally just so they don't have a date spread that could actually penalize an "authentic" car. The six months has no basis in reality, it is simply an arbitrary window that the NCRS guys figured would capture the time frame necessary to build 99.9% of the cars from beginning to end. Most times, the spread is two to three weeks or less. For instance, with big blocks cast in Tonawanda, the forging operation was adjacent to the engine build facility and many blocks were cast (casting date) on day 1 and built only a day or two later (engine build date stamped on pad). They were then stacked up to await shipping by rail to St. Louis and could have arrived anywhere from 2 days to 2 weeks later to be mated with their body. The body assembly date on the trim tag is when the body joined the line for assembly, but it wasn't actually completed until 1,2,3 or more days later, depending on weekends, holidays, etc. The "birthday" (not appearing anywhere on the car, but estimated depending on the VIN relative to the number of cars built in any particular month) is when she actually rolled off the line. This six month period also takes into account other dated components that may have sat on a shelf but weren't being pulled in any chronological order like glass, connectors, hoses, clamps, etc. NCRS wants all these dated items to fall within the 6 month period in order to provide full credit for authenticity, but again, it has little to do with reality.

 

As was already posted, the block casting date and engine assembly date need to be close within a few days. There wasn't any place to store block castings and they were asembled into application specific assemblies right away. Heads and other pieces can vary more widely from this somewhat but the casting dates of these other parts must preceed the engine assy date.

The wait for a finished engine assembly to get put into a vehicle will vary as the inventory was not first-in first-out. Keep in mind also that in general - the rarer the combination, the more spread you can see between engine assembly stamped date and vehicle assembly date. A batch of engines could be built for a rare application and it might be some longer time before they needed a new batch.

I have seen other accessories on a vehicle to have a much wider variaition in date code than the 6 month window but this rule of thumb is what the NCRS guides use.

-Mark.

 

NCRS doesn't generally date-judge components like heads because the casting dates are not easily accessible without dismanteling major components. The six month window applies only to items with dates (or specific change-over designs) and whose casting dates or date stamps are relatively accessible. Again, the original question deals with "why 6 months" by NCRS. If they don't judge them, it doesn't pertain to the original question.