I have a 1987 Z28 Camaro with a Quadrajet Carburetor, 5 spd manual. I recently found that the engine has a mysterious stamping code on passenger side behind the alternator. Here it is:




1MO828 4G35

It looks like the first 6 digits follow the standard sequence showing: 1 - check number, M - built in the Mexico plant, 0828 - built on August 28th. But then the last 4 digits do not follow the standard sequence which apparently should be 3 letters which make up the engine suffix code. I understand that the suffix code should also match the last digits on your VIN, which the 4G35 does not.

What is going on here??

I'm starting to think the engine has been swapped... The block does not have an opening for the mechanical fuel pump push rod. As I understand it, 1987 carb'd cars came stock with electric and mechanical fuel pumps.

 

I also have a 1987 305, but TPI, not carb, and I'm currently rebuilding my alternator, so I checked to see how mine compares to yours. I know mine is original because I'm the original owner, and the engine has never been swapped.

The top sequence, where yours has 6 digits, mine has 8 digits, nothing at all resembling yours.

The bottom sequence, where yours has 4G35, mine has 9 digits, with 8 of those 9 digits matching the last 8 digits of my car's VIN. And all of those same 9 digits are also stamped into my car's firewall (partially covered by the AC box).

That VIN sequence on the firewall is one of the major things DMV officials and/or police look for when verifying a car's VIN for background checks, state transfers, etc.

 

Doesn't look even remotely factory. Not their standard stamps (those are much bigger than what GM used), and not the same numbering format.

Looks like some machine shop stamped something or other into the block after decking it. Probably a work order number or some such.

If the block doesn't have the fuel pump setup completely machined into it, it's SEVERAL years newer than 87, and of course, obviously not original to the car. Don't want to get into "swapped", "rebuilt", etc.; I'll just let you do the math on that.

Post the block casting number (NOT the stamping "code") and the head casting numbers, and we'll help you figure out what you've got.

 

Possibly a GM goodwrench replacement crate engine? Seems like most of those were made in Mexico, at least recently.

 

Thanks a lot for the response fellas. Fireboyd, thanks for comparing your stamping numbers to mine. Hella crazy how different mine is....... I'm leaning towards crate engine now. Good thing I'm not restoring this car for the Pebble Beach Concours!

I'll go find those engine casting numbers and post an update here.