Altered engine serial numbers

[Curti]

In the case of  engine serial numbers being stamped at the factory on the top deck of a block and being removed during the rebuild process, then re-stamped at a later time.  Is there a process to bring the old numbers out.

[mike6024]

That would be similar to the situation of trying to recover the serial number from a gun used in a crime, when it had been filed off. Not easy. This article says simple acid etching may reveal some information, and very expensive scanning electron microscope it sounds like may get more information. The original stamping leaves some residual stress in the metal even below the actual numbers.

 

https://www.washingtonpost.com/national/health-science/scientists-develop-a-technique-to-find-serial-numbers-that-have-been-filed-off/2015/05/11/45e76fce-d489-11e4-8fce-3941fc548f1c_story.html?utm_term=.1401dadb634c

 

“Only two of the seven serial number characters could be restored” by his usual acid-etching techniques,

 

An alternative process under development since 2013 may fix this problem in the future. Using a technique called electron backscatter diffraction, or EBSD, researchers at the Boulder, Colo., campus of the National Institute of Standards and Technology have been developing a novel way to bring back to life numbers that have been completely sanded away. While the method, which uses an electron microscope to examine atoms in metal, still requires refining, NIST materials scientists Ryan White and Robert Keller say it should be capable of restoring a full serial number, even in such difficult cases as the Mossberg shotgun, in about an hour.

[mike6024]

Acid etching info

 

http://www.csitechblog.com/2011/07/how-crime-labs-restore-obliterated-serial-numbers.html

 

 When serial numbers are stamped into a metal surface, the metal beneath these stamps is compressed. When the numbers are removed, either by filing or grinding, a relatively smooth surface results. In many cases the perpetrator is satisfied that his task was successful if the numbers are no longer visible. But in reality, the compressed metal still retains these marks.

 The theory behind acid etching is quite simple: When applying an etching reagent, generally a strong acid, the metal around the stamped marks will be etched or eaten away by the acid leaving the compressed metal intact.

 

 One of the instructors in a well-known crime scene technology program tells the story of how serial number restoration saved him a considerable amount of money.

 This instructor was following up on an advertisement for a 1967 Chevy Camero with a 302 Cu. In. engine. He stated that if this vehicle was all original equipment, it would command the asking price of $19,000 (20-years ago). While visiting the seller and inspecting the car, he asked where the engine block number was located. The seller said that when the car was in for maintenance, a mechanic had accidently removed the numbers. HMMMMM!

The instructor, now somewhat skeptical about that bit of information suggested that he and the seller should restore the number and the seller agreed. Using the steel etching gel from his classroom, he made several attempts but the numbers did not reappear. He then decided to take a pass on buying the car. The next day the seller called and told the disinterested buyer that he had left the etching gel on the block for several hours and the full serial number appeared.

 Checking with the manufacturer, the seller learned that the engine block was a replacement and not original equipment, thus saving the instructor about $10,000!

[Curti]

Very informative  Thank you Mike !  

[Curti]

What is the trade name for the 'etching gel' ?