rmgny44

PO of my '72 claimed the car is numbers matching but when the engine was rebuilt the block was decked so the numbers on the pad are gone.
Is there any other way to check?

toylman

It's like a blackboard that's been wiped clean. Only thing you can check is the casting date behind the distributor and block cast number; rear left. Also, you can check the heads, exhaust manifolds, intake, etc to see if they may be the original components.

'75

Once those numbers are machined off, there's no proof, only some educated guesses related to date codes.

Alan 71

Hi r44,
The partial VIN sequence was stamped on the side of the front transmission case using the SAME stamp as was used to stamp the engine pad in St.Louis.
So, check there, if it's the proper transmission for this car you'll feel a little better.
Also, there were numerous parts on the engine that had part numbers and date code stamps or castings as Toyl mentioned.
I'll add carburetor, starter, alternator, distributor and fan clutch.
If at least some of those things are still in attendance it'll be a good thing!
Regards,
Alan

Casting date location. L 31 0…. December 31, 1970, for a mid-January built car.

69Vett

standard machine shop DECKING, REMOVES YOUR ORGINAL #'s
Never do this with an original block, you just lost your matching numbers motor.

cv67

Kind of late now any reason to believe it isnt the original?

Did you pay the "numbers match" tax

Personally wouldnt worry about it at least you know the deck is flat

BKarol

An alternative location for the vin derivative is near/aft the oil filter & is mentioned in my NCRS judging manual. They point out it is "RARE" but some have been observed. Not a flat surface like the stamp pad but worth a look while you are scanning the transmission.

ddawson

Did you remove the paint? With it completely done I bet they zero decked it.

Best way to make sure it's flat and straight. Pretty much all the machines shops by me won't attempt to leave the numbers. You either deck it flat or they won't touch it.

rmgny44

I'm not too concerned just curious! It's not an investment I bought the car to drive it. When I'm too old to get in and out my son gets it !

7T1vette

If the machinist didn't take off too much stock from the block, you might still get lucky. You can apply nital etch (nitric acid and alcohol mix) to the metal surface where the stamp used to be. Afterwards, you might be able to make out the original numbers in the etched surface.

When the numbers are stamped in the block, the metal under the numbers is 'work hardened' and becomes harder material than the other metal surrounding the numbers/letters. The etch "eats" the softer metal a bit faster and there is a discoloration difference that you MAY be able to detect.

I wouldn't recommend that you do this with a pristine pad...but, unless you can convince yourself that the engine is original, I would have to assume that it is not.

If you want to check out nital etch, just do a Wiki on it.

P.S. If you do this and the etching shows the correct numbers, take some high quality photos of the process and the final surface. That way, you can demonstrate that the engine in the car IS the original engine...even though it has no stamped numbers on the pad. There might still be someone out there might accept that evidence and still pay you a premium for a numbers-matching car. [doubtful...but possible]

Easy Mike

True, but almost certainly not applicable to the OP. The alternate location was to be used in the event the assembly line worker could not get a legible stamp on the block pad. In the case of the OP, the factory pad stamps were good until the block was decked.

crf311

once the numbers have been machined off, you can only say numbers matching. As far as saying original, that proof has been machined off. IMHO

gungatim

if the FBI can use some sort of chemical to view filed off serial #'s from guns used in a crime, seems there ought to be a way to do the same with an engine block...my block was decked and vin portion removed and maybe 35% of the engine stamp is legible. would love to find out if it was original too.

best I could ever read with a magnifier was T 10 11 IU which would be oct 11 date when the car was Nov 14, which would jive. only problem is my tank sheet lists L71 but the IU indicates L89, even though I 've obviously got '67 alum heads....the mystery may never be solved...

Alan 71

Hi g,
Are these some digits?
Anything correspond to your VIN sequence?
Regards,
Alan

vettebuyer6369

Actually, once the numbers are machined off, you can no longer say numbers matching.

Numbers dont prove originality. Numbers are restamped all the time.

68post

The above mentioned acid method is how law enforcement determines number stampings on castings.

drwet

Al Grenning has developed a database of factory stamps which can be used to compare a block stamp to a known original. When the factory stamped a block with the VIN, they would use the same stamp on every car, just changing the last digit. Therefore the stamping on two consecutive cars on the assembly line would be virtually identical, with the exception of the last digit. He showed me some of his collection years ago, and its pretty cool. If its a valuable car, he can often provide confirmation of an original block. If its not a particularly valuable car, who cares?

mrvette

YUP, sure are.....found that out some 18 years ago down at NCRS Orlando, from some club members....

rmgny44

Can anyone translate my transmission ID tag.

top stamp
72K 347

lower stamp

72 CK 6550

GOSFAST

I would just add some info here with respect to decking these OEM/numbers matching builds. For years we've done "tons" of these resto's and have always "squared-up-the-decks" and NEVER removed a single original digit, not a single one.

We've milled as much as .025" off numerous builds and still never lost an original stamped number. It's easier today than in the past but we still managed to get it done back then also! You just need the right equipment?

Thanks, Gary in N.Y.

P.S. When you begin the build process make absolutely certain the machinist is aware if it's an original numbers deal and if they have ANY issue with getting it done correctly, move on to another shop!