Curious about 72 LS5 component dating

[Mike E.]

I'm dealing with a 72 built October 18, 1971. I've been able to trace all the owners, because small towns don't pay much attention to privacy laws. None of the previous owners knew about or cared about numbers. 93k miles, original motor, trans, rear. Starter and radiator have been replaced. Motor is cast August 30, assembled September 9. The carb,,smog pump, fan clutch, alternator, fan blade, brass expansion tank, intake, flywheel, AC compressor, jack, radio, flashers, wiper motor, horn, door panels, seat belts, shoulder belts, wheels, spare tire, etc. are all dated in expected fashion.
The two-page purple carbon build sheet was rolled up under the dash and I have had it NCRS-validated.
There are a few components that I have questions about. I've not played with big blocks, but as many of you know, I've written several dating articles for NCRS on small blocks.
I would appreciate input on the following:
The heads are dated acceptably for a September 9 motor, June 28 and July 6, but they are 3993820 casting numbers, which are correct for 71, not 72. Any thoughts on that?
The exhaust manifolds are the correct casting numbers (which are the same for 71 and 72, but casting dates are April 16, 1971, and December 15, 1970.
The distributor is a correct 1102051, but is dated January 26 of 1971.
None of the previous owners (I have talked to 2 of the 3, and the middle one who is lost only owned it for a year and the other two said he did nothing to it except drive it) are aware of anything being done to the car except replacement of a flat cam which was done by owner number three himself.
Thoughts you have about why the distributor and manifolds are not in the normal timeframe and/or why the heads are 71 casting numbers?

[Mike E.]

Re: Curious about 72 LS5 component dating

Anyone with ideas of what could have happened in production?

[Bob D.]

Re: Curious about 72 LS5 component dating

Mike

I'll throw my 2 cents in here and suggest that because it is a big block, GM may not have used those components as quickly as the small blocks and that could be the reason some of those components are outside the normal range. I have a '71 big block with a November '70 build date. The heads are dated April. Now there was a 2 month strike in '70 that could account for that. Terry M may have some additional info as he is the one who told me that regarding my car there were 4 others with similar dates. The '71 casting numbers on your '72 may have been a result of left over parts. GM never threw anything away that they could use. Again, on my early '71 I have '70 tail light lenses, '70 horn button and a 5 port washer pump. Hope this helps.

Bob

[Patrick H.]

Re: Curious about 72 LS5 component dating

None of the dates or number are surprising other than the exhaust manifolds. My June 71 car had an August 70 water pump, and I strongly believe that parts were used when they showed up on the line. They may have been in a back room or storage area for a long time before making it out, and the line worker really didn't care.

The 6 month rule is a guideline, not an absolute.

[Mike E.]

Re: Curious about 72 LS5 component dating

Bob,
What are the last 4 digits of your vin? A bunch of years ago I did a dating article on 71 #2485, a November 70 LT-1 car. If I recall, there were less than 500 made in November of 1970.
Thanks for the input, Bob and Pat.