Quote:
Originally Posted by 72projectbird
My 3rd week of March 70 has its original engine, which was built in January of 70.
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Not to pick on 72projectbird's response but to use it to illustrate an important (in my view) point.
Engine blocks have cast date tags. These tags represent the date that the block was cast.
It does NOT represent when the Engine was assembled in Pontiac's one and only engine plant located at the Pontiac, Mich home plant. One should NOT use the block cast date to indicate when an engine was "built".
The EUN can be used to establish the approximate date that the engine was assembled.
Perhaps it can be done more easily but I have spent years collecting '64 engine data (when partial VINs were not yet added to the block at final assembly as a theft deterrent and the year Pontiac quit stamping the full VIN as they had for some years through the '63 Model Year). From the data I can generally figure out the expected cast date and EUN based on the Time Built code on the Data Plate. I've been able to establish a decent correlation between EUN, block cast date, and Time Built code for '64 Pontiacs. And there are always anomalies that fall outside the expected ranges. Only thing certain, the block used in the original engine was cast before the car shipped.
What I have noticed over the years, these general correlations seemed to hold up pretty well throughout the '60s.
But starting with the 1970 Model Year, the correlations have seemed to be far less predictable.
I don't know if I've ever discussed Norwood's '70 engine. My knee-jerk reaction, I'd be curious to know if his EUN shows an engine assembled many months before his July TA was final assembled or if the EUN shows a late assembled engine assembly that happened to make use of a much earlier cast block.
I have encountered rare examples of both scenarios from the mid '60s. Neither scenario would surprise me and perhaps both scenarios were more commonplace beginning in '70.
The stamping of the partial VIN on the block adds another data point for '68 up engine assemblies which can be helpful in detecting restamps and other mods that attempt to disguise a NOM as original.
I wrote the above but forgot to post it yesterday. And now I see Norwood has posted his EUN.
Without benefit of significant data, it looks to me that his EUN was assembled around early Feb. If this was a '64 engine assembly, it would be unusual (but far from impossible) for the block to have been cast 2 months before it was assembled into a complete engine assembly. And also unusual for the completed engine assembly to have sat in Final Plant inventory after arriving at the Assembly Plant for some 5 months before being installed into a car build.
The latter, IMO, did occur more often at the end of Model Year production precisely because the Plant tended to operate somewhat on a First In, Last Out inventory control. That is, engine assemblies arrived in "bulk" and were placed into some form of inventory. As they were being used up in production, the next batch of engine assemblies arrived, burying whatever inventory remained.
At Model Year build out, inventories of everything (in particular, components that would not be carried over to the new Model Year) would be drawn down.
At that point (typically July being the end of MY production), engine assemblies that had long been buried at the back of the storage location collecting dust got uncovered and pulled for a build.
All speculation, but that would be my explanation for how this Feb assembled engine assembly became original to a 7C build at Norwood.
A similar explanation could be used for why a mid Dec '69 cast block wasn't made part of an engine assembly until Feb '70 based on how block castings may have been stored at Pontiac, Mich either prior to machining or engine assembly after machining.
As I mentioned, such disparities were never unknown but they do seem to have become more common after the '69 MY just by anecdotal evidence that I've come across thru the years.