if the matching VIN derivative # is not visible on the engine pad,
1 can only conclude = Not original engine.

often a motor gets rebuild /decked = removing the top layer off the block.
this often will remove the number your looking for.
it is smaller and not stamped as deep as the engine code. #.

 

I believe there is no significant deduction if the replacement block has the correct casting number AND date code is within 6 months prior to the build date of the car. I've never heard of a replacement block being passed. The concept being the component must appear as it would for a typical build at the time the car was produced. A block with a later date code wouldn't make sense... Others, please feel free to correct me if I missed something here.

 

Interesting discussion, but why not start a new thread? The original closed out in 2013.

 

Ok, I gotta jump in here.
I have what I believe to be a factory 5year/50,000 mile warranty replacement shortblock to the best of my knowledge through research and comparison to other like vehicles.
An over the counter engine....427/390hp engine came with an inventory control number stamped at Towanda foundry only.
Did some dealers have their line mechanics cold punch a vin# in the replacement blocks for the purposes of federal guidelines?
Possible, but you would still see the otc Towanda control # to the left.
They would not stamp another block date on an over the counter GM engine replacement partial.
Someone blew mine up! The dealer took the top end off and placed it on a GM replacement partial.
These came with everything installed in the lower end minus the pan.
I worked at GM and unpacked these things.
The line mechanic got 8 hrs to remove the engine, swap over the orig. top end and reinstall. No one ever made the time.
I remember guys bitchin everytime they drew the shortblock short straw.
I believe you engine was in a production line car.
Some one removed the original vin# but saw no harm in leaving the date stamp on the pad.
R/S across from the starter should be a casting number.
This is when the block was made.
All my parts for a June built car are April, May dated.
There was no strike in 68.
Everything w/in reason is usually 3 months out.
They restocked the bins as they emptied them.
The TR bolt thing is kinda funny as when the factory was short they
used whatever supplier was avail.
Most cars I think are judged based on only several orig examples documented and used as a bench mark.
Sometimes everything didn't go as planned that day on the assembly line.
Marshal

 

I was standing next to my friend when he called a person named Gary from NCRS. The conversation they had went something like this:my friend said to Gary that I had a 68 427 with a stamp pad number and no vin number on the pad. Gary quickly surmised that it was probably a short block from the warranty warehouse. The blown engine was probably under warranty and Chevy replaced it with this short block . My friend then asked him what effect this would have on the judging of the car and the answer was little to no effect. I guess you could call that a mulligan or a free pass.

 

I have older friends that were Chevy Mechanics during the late sixties through the eighties, and they tell me you will not believe how many "matching number" cars were blown up racing Friday through Sunday. They used to hate coming in on Monday bc there would always be 2-3 cars with cracked up motors. Especially Corvettes and Camaro's. My 68 is a recipient of a CE block, I do what these guys tell me, just DRIVE the damn thing you big dummy!

 

The Judging Guide lists a 25 point deduction if the VIN derivative stamp is missing or incorrect provided the block and required casting numbers and dates have passed requirements. You can decide whether 25 points meets the definition of "little to no effect."