Engine ID wild goose chase

grcthird · Apr 21, 2016

So...I am working on a rat rod for a body shop, VIN is an 84 firebird, body has been cut off and an old chevy truck dropped over it. It has a small block chevy in it, 400 crank, 350 block .040 over, I got to checking engine ID numbers and stuff wanting to figure out what it came out of.. so far this is what I have;

Casting number 3970010 block number on left rear of block, nothing special, GM made a gazillion of them, may have 4 bolt mains, (probably does, haven't verified yet, waiting on my borescope to show up for a month now :

)

Engine ID stamped on right front of deck is V0912CJM, figured out V=Flint MI plant, 09=Sept, 12=12th day of Sept, CMJ has 1 option in this case, 1974 police car (Yes there other CMJ options but not for the year)

Partial VIN stamped on it is 15J118534, 118534 is a sequential number from rolling off the assembly line and apparently there is no way to determine what the car is by this, J=Janesville WI plant, 5= year of vehicle 1975, 1=engine, more specifically what HP it had and displacement, but nowhere can I find anything about a 1 engine code, all GM 1975 engine codes are letters, this is what is driving me crazy.

Did GM build engines at the Flint plant and ship them to other plants for installation into what ever vehicles? Would a Police car engine have it's own designation outside of all the other engine designations? I'm guessing the date difference would account for the engine being built in Sept 74 then installed in early 75? The Janesville plant made fullsize cars that would be used as police cars, my best guess is that it was in an Impala.

None of this really matters, I just think it would be cool to know what it came out of. Maybe the block got decked sometime and somebody stamped bogus numbers on it to :flipoff1:

with me

Anybody got any other ideas?

jwilson645 · Apr 22, 2016

I'll post the info over on the 73-87 truck board. there's a guy there that worked at GM for a looooong time. I'll see if he knows anything.

pholmann · Apr 22, 2016

Aren't all 010 blocks 4 bolt main?

417chevy · Apr 22, 2016

pholmann said:
Aren't all 010 blocks 4 bolt main?

The majority but not all

grcthird · Apr 22, 2016

pholmann said:
Aren't all 010 blocks 4 bolt main?

From what I have been reading, not all are. Bore scope showed up so I maybe able to peek in there later today.

4byfan · Apr 22, 2016

All of the 010 blocks are defiantly not 4 bolt mains. I've built a bunch of 010 2 bolt mains.

jwilson645 · Apr 26, 2016

J, here's what I got back from the GM guy.

I agree with his Engine ID breakdown. I did find a website indicating the following additional usages for a CMJ code (it does not say where they got their info):

CMJ 75 350 Impala 145 L-65 TH 350 2-Brl A.I.R.
CMJ 75 350 Chevelle 145 L-65 TH 350 2-Brl A.I.R.
CMJ 80 305 Impala 155 LG-4 TH 350 4-Brl

He is correct – the partial VIN does not give any information what car that is – but – some clever deductive skills and knowing what products were produced in that facility means that the VIN prefix can be reconstructed in most cases. Police engine part number (and broadcast code) are assigned right along with all the other more pedestrian engines. Some discussion about the assigning of part numbers and broadcast codes here: http://67-72chevytrucks.com/vboard/s...ght=TAB&page=4

The "1" in the partial vehicle VIN designates the Chevrolet nameplate, not the engine code like it does in the full VIN.

Fint built all of the small block engines and shipped them to the various vehicle final assembly locations. The V8 plant is stilll in operation and is located at the corner of I-69 and I-75 in Flint, and is co-located with Flint Assembly (the truck plant where I started) and the Metal Fabricating plant ("Metal Fab" – produces stamped sheetmetal components like fenders, radiator supports, etc).

As a result of all this I agree the car was likely an Impala.

K