Running engine vin numbers on side of 307 block

[tobyp]

So I have a real good mystery revolving around an engine which is a OLDS 307.

The numbers are 3CM253487 which the terminology in the letters has me way off

Anyone out there that knows how to determine the date code on the engine from the VIN advice/information greatly appreciated. ALL olds websites about block identification has the numbers starting with a (3) oldsmobile; then a number...1,2,3, etc representing the year; and then (m) meaning made in Lansing Michigan Plant; then the serial number of the car. As you can see mine is (3); (C); (M); 253487.

BTW THis is a 81-85 engine since the casting number is a 3161-5a, the block on the side is a 5L (307) with 5A heads.

I have a couple codes near the distributor that I cannot find any information that I have no clue what they represent

right below the distributor is CFD and to the right side of the distributor is 69

 

[Evan11]

If it has 5a heads, its a 1980-84 non roller engine or 1983-1985 vin "9" Aka high ouput 307. 85-up "y" engines had 7a heads & were a roller engine. Your intake manifold should have "A4" stamped on the front left side (drivers side.) 85-up "y's" had smaller ports & its own unique A5 intake. CFD stands for central foundry. A lot of my family worked & still do work at the GM central foundry plate in Bedford, IN. Here's a link for 307's, so you can get the exact year. http://www.442.com/oldsfaq/ofe307.htm. I couldn't find anything with the #'s provided. Are the exhaust manifolds marked?