Date code question

[Jmoore9622]

I have looked over the site information and tried to search the forum but couldn’t find what I was looking to find. I was wondering an approximate date range for a block if the numbers matching transmission is a P8D27 date code? 05A ‘68. Anyone have original drivetrain to put a ballpark timeframe on it? I’m sure it’s not a set date due to factory operations, delivery times, SNAFUs at times, etc. Thanks for everyone time and input in advance.

Joe

[bcmiller]

Do you believe the block you have is original? If so, what is the casting date and what is the assembly date and 2 letter engine code?

[69Z28-RS]

Since the engine and the trans are produced and delivered to assembly by different plants, there's only a very loose correllation between the respective date codes in a given car.   You'd be more accurate to use your VIN assembly date (for the car), then project backwards the 2-weeks to 2 months possibility for the engine assembly, and there could be even more disparity than 2 months (in rare cases).   If you are searching for an engine which is compatible, then try to find one that is 2-3 weeks before the car assembly date (as determined by your VIN.

[Jmoore9622]

Block is not original to the car but was an early April date code MO block. My dad made a trade years ago, he traded an original cowl hood for the block. Unfortunately it was decked when he sent it out.

[69Z28-RS]

JMoore,

If you are looking for a 'date' in order to restamp your decked block, I would STRONGLY recommend you not do that as that will LIVE with the car forevermore, and it's detectable!

If you KNOW the block is a correct MO block, then be happy with it.   Record the casting date (from the rear of the engine) which should be close within a day or two prior to the assembly date.  Record all this along with your personal information that your dad decked the block which removed the application stamp and VIN information.  My personal opinion is that I'd BUY the car from you (if for sale) with that story, but I would NOT buy the car from you having seen the restamped codes!!

Your engine casting date will be close to the assembly date, and early April is 'ball park' close for the 5A assembly approximation.

[bcmiller]

I agree with Gary.

[Jmoore9622]

Never was considering that i was just curious what it might have been. Also for general knowledge to inform others. My dad taught me to never misrepresent anything in this hobby. It’s been decked since the 80’s, it’ll be decked once he passes it to me, and once my son is old enough to understand things it’ll stay that way long after I’m gone. No worries here. 🤙

[bcmiller]

Let me try to do some checking... 

[MO]

I recall reading a post that described a method that might allow the original stamping to be seen if the decking wasn't too deep. I can't find it, but maybe someone else remembers this and can help. Something like a muratic or citric acid treatment maybe?

[z28z11]

Nitric acid to etch the surface around the compacted stamp contact areas. Law enforcement has used that to "raise" serial numbers on weaponry after they have been removed -

Have you applied to the NCRS for a build/release date for the car ? I believe it would help pinpoint the time frame you are trying to establish -

Regards,
Steve

[Jmoore9622]

Yes, he has the paperwork at his house. I’d have to over and look at it for the dates but everything lines up from when we went over everything. If i remember right it was built May 5th and delivered May 16th(could be a day or two off) along with his trans date of April 27th. I was off work today drinking coffee and just reading the site section talking about how the blocks were cast and assembled. Really interesting how the pistons went in btw, anyway just always love reading and learning history on these cars. Curiosity got to me🤙

[Jmoore9622]

Clarification*** documents obviously didn’t give trans date that was already know prior.

[Stingr69]

Blocks do not sit around for long periods of time before being assembled.  They would be cast and assembled into some application fairly quickly between a day and a week or two on average.  Once assembled, it would be assigned to the vehicle "as needed" but that would vary depending on supply and demand for the application.  High volume applications would typically be used quickly while less common applications could sit for longer periods waiting for an order.  NCRS manuals have guides that ally to Vettes but that does not mean that station wagons would follow the same routines.  Still, a good place to start.