Re: Mecum Auction 68 L89 Camaro
 

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: bergy</div><div class="ubbcode-body">Maybe you could post a picture of the thermal image of an actual block stamp. Metallurgically, I guess that the internal stress could impact the heating/cooling rate very slightly. I don't understand why the thermal unit would pick up a stressed area in the absence of heat change though. Worth a try - show us what you have observed. </div></div>

Because there is NO WAY for a &quot;forger&quot; to duplicate the properties of the metal in the original mold, thermal IR will show the difference in the properties of the metal. In addition, one would have to grind the original stamping (which would also change the properties of the original metal and show up on thermal IR), then build the area back up, presumably via a weld, stamp the new numbers, and then &quot;clean up&quot; the entire area around the new numbers. Frankly, an exhaustive process, but one that puts a significant amount of stress on the original casting, as well as adding new material with different properties. Here is a thermal IR image of a common weld, cold (no heat applied).
https://www.yenko.net/ubbthreads/pics...-4763-weld.jpg

If you imaged the block while hot, it would be even more pronounced but as you can see, heat is not needed to detect a weld. Believe it or not, a weld will also cause a very small amount of moisture or sweat, even though you can't see it. Here is a thermal IR image of moisture trapped in the metal.
https://www.yenko.net/ubbthreads/pics...4764-water.jpg
Sometimes, you don't even need thermal IR, although, I think it's more accurate. Here's an IR scan of a &quot;clean&quot; weld (one that has been fully worked/blended with the original material.
https://www.yenko.net/ubbthreads/pics...24-4765-ir.jpg

Re: Mecum Auction 68 L89 Camaro
 

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: bergy</div><div class="ubbcode-body">Maybe you could post a picture of the thermal image of an actual block stamp. Metallurgically, I guess that the internal stress could impact the heating/cooling rate very slightly. I don't understand why the thermal unit would pick up a stressed area in the absence of heat change though. Worth a try - show us what you have observed. </div></div>

Sorry Bergy, regarding an image of an actual block stamp, we've never done that, but the same principals logically apply. And frankly, an educated guess tells me the people who fake blocks/stampings aren't nearly as careful/skilled as those we are after...

Re: Mecum Auction 68 L89 Camaro
 

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: twertsy</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: bergy</div><div class="ubbcode-body">Maybe you could post a picture of the thermal image of an actual block stamp. Metallurgically, I guess that the internal stress could impact the heating/cooling rate very slightly. I don't understand why the thermal unit would pick up a stressed area in the absence of heat change though. Worth a try - show us what you have observed. </div></div>

Sorry Bergy, regarding an image of an actual block stamp, we've never done that, but the same principals logically apply. And frankly, an educated guess tells me the people who fake blocks/stampings aren't nearly as careful/skilled as those we are after... </div></div>


I do not believe there is any welding done on the block re-stamps. They just grind them enough to remove the existing numbers and re-stamp the new machined surface.
Does that machine work to show prior stampings below the grinded surface. I assume the metal molecules are somewhat crushed deeper into the metal when it is stamped..?? I once contacted a 'scientist' about a ZL-1 block who mentioned about 'etching' the metal??

Re: Mecum Auction 68 L89 Camaro
 

I do not believe there is any welding done on the block re-stamps. They just grind them enough to remove the existing numbers and re-stamp the new machined surface.
Does that machine work to show prior stampings below the grinded surface. I assume the metal molecules are somewhat crushed deeper into the metal when it is stamped..?? I once contacted a 'scientist' about a ZL-1 block who mentioned about 'etching' the metal??

I'm not familiar with &quot;etching.&quot; Unless he was talking about them using etching to fake the stamp/numbers. In which case, that could also be detected.

So, several things: first, if the above is their process, I would think precise measurements would reveal that process, given known blocks were from the same mold. Second, if measurements aren't reliable, infra-red would be very likely to reveal remnants of the original stamp underneath the fake. Lastly, if you had a thermal infra-red image of a known real block (after heating), then compared that image to the one in question (again, after heating), you would see anomalies in the &quot;worked&quot; area. You MUST image them from the exact same angle however.

Re: Mecum Auction 68 L89 Camaro
 

Pretty soon you will have to be a nuclear scientist to authenticate a car...what a shame. [img]<<GRAEMLIN_URL>>/no.gif[/img]

wilma

Re: Mecum Auction 68 L89 Camaro
 

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: WILMASBOYL78</div><div class="ubbcode-body">Pretty soon you will have to be a nuclear scientist to authenticate a car...what a shame. [img]<<GRAEMLIN_URL>>/no.gif[/img]

wilma </div></div>

Particularly for us &quot;newbies&quot; to the hobby who don't know all the stuff you guys do......and getting ripped off.

Re: Mecum Auction 68 L89 Camaro
 

Ok, so I just spoke with our Chief Scientist (PhD Physics). He says that it would be easy to tell a re-stamp with a thermal infra-red camera. Here's the process:
1. Start the engine and let it get hot
2. Turn the engine off
3. As it cools, take an image every 15-30 seconds
4. Compare the images (visually inspect them)

According to him, the old stamping will be revealed at some point during the cooling process. He says there is no way they could grind away enough of the original stamp without it being blatantly obvious.

So there you go.....
[img]<<GRAEMLIN_URL>>/biggthumpup.gif[/img]

Re: Mecum Auction 68 L89 Camaro
 

the guy in florida has ORIGINAL BLANK PLATES not newer plates and nos protecto plate booklets. He isnt the only person who has them either. Every thing on these cars has to be checked out. I am making no statement about the L-89 in this thread. i dont know anything about it. I could talk about gas tank stickers and dealer order forms. They counterfit those too. iF I WAS BUYING A 200K CAR I WOULD WALK THOSE DOCUMENTS UP TO A HISTORICAL DOCUMENT EXAMINER . i KEEP A REAL TANK STICKER IN MY COLLECTION FOR REFERENCE.

Re: Mecum Auction 68 L89 Camaro
 

If anyone near Northern VA has a known re-stamp, I'd be glad to arrange a test with a local vendor of thermal IR cameras. Alternatively, someone could walk me through the process of creating a re-stamp in iron / aluminum (tools, dies, whatever would be needed) and we will test it. I'll post the detailed results on what exactly it would look like so you folks have the info.

Re: Mecum Auction 68 L89 Camaro
 

Of course, there are some &quot;virgin&quot; over the counter blocks that have original broach marks. These would not have to be ground to stamp them. One well known 67 L88 that lost its motor has a correct build stamp long block in it. The person that had the car restored years ago chose not to stamp the VIN on the block.