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My 67's engine pad is decked. The only think I can make out is the IL for the 427/390 and the numbers 10. I have heard that muriatic acid, stuff coin collectors use to pull the dates from coins might work. Anyone have any suggestions about what to do, or any ideas on other avenues to determine if the engine is original to the car?
Thanks,
Chad
Properly performed by someone knowledgeable in the process, the original numbers could likely be raised using the acid-technique that you describe. However, such a process will not RESTORE the original numbers to the pad in any sort of a permament manner. This is just a process to determine what the original numbers were. Usually, this process is used in forensic science but it can be used for other purposes.
In your case, you can still see the important part of the engine stamp pad coding (i.e. the engine suffix code), so you know what the engine originally was. However, the process mentioned might be able to raise the original VIN derivative stamping so that you can tell if the engine is original to the car. It will be somewhat academic, though, since, as I say, the process won't permanently restore the numbers. You'll still need to restamp the block to permanently restore the stampings.
It will be difficult to restamp or "restore" the engine stamp pad and stampings in any meaningful way unless you can restore the original broach marks, which will be difficult, at best.
I would find someone in the police forensics unit who will explain the acid process in detail first. I don't believe the police use muriatic acid on guns. I think they use something stronger like nitric or sulfuric acid. I do know they first smooth the metal with sandpaper. The stamped characters appear after several minutes of wiping with the acid. The stamping is actually raised above the surrounding metal that is dissolved at a faster rate. Your original stamping will appear as raised, lighter colored metal. The characters will not recede after you neutralize the acid, but the lighter coloration may disappear.
Another choice for raising the stamping is high heat. This method has many drawbacks. The characters will be pronounced enough to read when hot, but they will be less noticeable after the metal cools. You also have to have the head off or risk ruining the gasket.
Whatever you decide to do, I sugggest that you not "restamp" anything. That will only obscure forever what the factory put on your block. Also, it will provide fodder for many heated arguments several generations from now.
If the block is decked, and the broach marks gone, then finding the original numbers by acid etching will still lead to a hassle in judging.
If you have new broach marks put on, then you have to have the block stamped anyway so it really doesn't matter if it is the original one or not.
If you are not judging, then you don't have to worry about any of this.
If it is for selling, then unless it looks like the 90% of all blocks out there, the potential buyer will reject it as non-original and won't pay extra no matter what you tell him or show him.
If you think the car runs better with the right numbers, it does. However, the right numbers are usually the ones like 327, 427, 12.6, 4160, 3.70, and not ones like T0915IL.
So really, it is only to ease your thoughts on originality. And it will definitely damage the block so that new broach marks and new stamps will not be a choice in the future.
If you were me, I'd forget it. There is essentially nothing to gain.
If it were me I'd go for it! If you care [I would] it would be great fun to know if it's the orig engine. If others don't belive you, I would not be concerned. It's your car and your not doing this to impress anyone but yourself [I hope]. On the matter of eliminating the chance of re stamping the block, I'd much rather find out it's the real thing for the satisfaction of knowing, instead of re stamping for some false satisfaction. If you are planning on having it judged tho, you'll have to consider Mikes suggestion. And I suppose there is the dollar consideration by re stamping and passing it off as the orig.
Original engine blew up in the 60's, replaced with carefully found correct year block with similar date. Replacement engine needed 1 more letter to pass for original. Never gonna do it- I get more pleasure out of the effort it took to get the engine "right". Having the original requires only luck.
I went through this same thought process with my 67 L-79 and decided to leave well enough alone. My pad was left with enough info and along with the casting and date codes on heads, block, trans, and rear end I'm convinced I have an original. For some that may not be enough. I still love this old car.
I did this to a rare L89. I was the 2nd owner and felt that the block was original - the first owner stated that a Chevrolet warranty repair for a valve issue led to the decking of the block (they did not care about these things in those days). I wanted to "know" whether or not it was the original block so I did the acid treatment. Search the oldest Archives, or the 2nd oldest under my name - you will find plenty about the procedure. I found the numbers, and recorded the entire procedure with still pics and tried some video, but the numbers you will see are quite faint - the pics show some but the video did not. My intent was to RESTORE the pad if it was the original block, which it was. The more rare the engine option, the more value there is to having the original block. I had witnesses on hand for the procedure and was going to have letters signed and notarized, describing the procedure, the recovery of the original stampings, and the RESTORATION of the stamp pad (I never intended to hide the fact that the pad was restored). I ended up selling the car before the project was completed, but I would do this procedure again (in the same circumstances, with this same car).
Thanks to all for your responses. Still not quite sure what to do, though. Casting numbers, etc. all point to originality, but I'd still like to think there is some way to be 100% certain for my own satisfaction. I would like to get it judged at some point, but not sure how the decked pad will affect it. I would not, however, consider restamping simply because it is part of the car's history. I think if I do go with the acid, I'll proceed along the lines of what Everett wrote. Thanks again to everyone.
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