Hello All  - I found some numbers while cleaning under the hood and was wondering if anyone could help decode:

- Back of block by firewall on drivers side: 3970010
- On manifold behind carb at cap: 3997771 gm2 (?)
- Underneath cap and rotor very hard to make out: c163 (?)

How can you tell if the engine is original to the car?

Thanks in advance!

Jason - not sure about the c-163 you found in the distributor, but the other two are the GM casting or part numbers for the engine block and the intake manifold. The good news is that both numbers are correct for a '73 small block. 

How cool that you can figure out all the way down to the date the car was assembled by decoding these numbers!! Thank you for the information and what/where to look for more. Going under the hood today and will try to search for more numbers! This is like being a detective! :)

in the state of conn  have to show 5 vin numbers,eng,trans,frame,windshield piller,inspector stopped at 4 said that enough   I got my res   plus have vid title      alls well here in conn.in florida I had to bring car for vin check with a valied tidle   alls well in fla   dwa.

Ok found something awesome!

My VIN # is: 1Z37J3S418986
The numbers stamped onto the block on passenger side in front of the head are: 13S418986
(I think the "1" is supposed to be a "J"...but it really looks like a "1" on the block.)
Looks like I have a matching numbers car?!  Woo Hoo!!

Back of block passenger side by firewall looks like C80, but it nearly impossible to decipher.

Unfortunately the extra numbers stamped by the 0010 number beneath the driver's side valve cover right behind carb are impossible to see or get to. 

The C163 on the block behind the distributor is the casting date of the engine block....March 16, 1973.



This is the day the engine block was cast....NOT when the engine was assembled. The block would still need machining before assembly, then it would be shipped to the assembly plant for final assembly, which could have been a couple of days, or weeks....or more.


13S418986
The "1" in your partial VIN is definitely a "J", which tells us it is an L-48 engine.
3= 1973 year model
S= St. Louis assembly plant
4= check digit...means nothing(well, it does, but not for our purposes)
18986 is your sequential build number, meaning the 18,986th Corvette built for the 1973 model year.  

Thank you for the diagram, Adam!  Definitely printing that out for reference!

Here is the best pic I could get of the numbers.  It's a "4" and to me, what should be a "J" looks like a "1".  Is this not normal?  Or are they just too close in appearance?  But you are correct, the engine is an L48!

Jason, don't worry about the 1 and the J, I believe all of the engine stamps started with a 1 and did not match the letter in the VIN. My engine stamp starts with the same 13S while my VIN reads T3S. So beyond the VIN stamping, what other numbers did you find ?? Those should be a slightly larger font starting with a V then 3 or 4 digits which are your engine build date. That should be followed by a three letter code indicating your eng/trans option.

Thanks VMan, for the reassurance regarding the "1" and the "J". The other set of numbers I found, the larger font, is as follows: V032 CLC. between the 2 and the C, there is an etching that looks like a square. Not a zero but to me looks like a square. I also found back by the firewall passenger side, what looks like C80. Impossible to tell for sure though...

Interesting, the V is correct for Flint, the 032 may indicate a March 2nd, 1973 engine build date, but I think the zero or square you mention between the 2 and the C in CLC might make it 0320 or a March 20th, 1973 build date. Looking at mine they clearly stamped 06 to indicate the 6th of Dec., I would think March 2nd would read 0302 but I could be wrong. The CLC suffix is correct for a 1973 350 cu.in., 190hp, at, ce which means your car was built originally built for California Emmisions, perhaps you have an original CA car !! Do you have any history on where the car came from ?? While we're at it, take a look at your body trim tag (right next to drivers side top hinge with door open). There should be three sets of numbers, the first is a three digit code that indicates the interior trim type and color, the second indicates the original exterior color, the third is in the top right corner and indicates the month and day of the body build date. That may give us another clue if your engine is a March 2nd or March 20th car. My body build date seven days after my engine build date.

|UPDATED|7/3/2015 10:41:06 AM (AZT)|/UPDATED|