I'm a newbee to the chevelle world and I have some weird codes on the block that I have been unable to ID. Wondering if anybody knows what they mean. the stamp on the front RH is K03250 NU on LH rear it has a raised echting 8970010 M6 and on the RH rear a metal plate rivet to the block 55728/5.

it's a 72 chevelle 350ss. those codes don't make any sense from what I have read.

any info would be appreciated.

the raised etching is actually the casting number. it's 3970010, it's likely to be a 4 bolt main. The tag riveted on usually means it was rebuilt at a big re-man plant. I don't know the engine code but somebody here does.

thanks that helps. what about the "NU"???

Ok. So after a little more research the block code seems right but I cannot find any instances of a 350 motor with the suffix "NU." I was told this was a police car. Would that make a difference. Thanks in advance.

Doubt the NU is your engine code as that's a '61 283 Truck engine.
Now CNU is a '70 350 from a full size.
Care to look again ?

my block off my 71 elco has VO then 3 numbers then ckr. is that the original engine?

As you didn't specify SBC or BBC ,heres all the choices.
If SBC ,narrow it down by the block casting date.
Any of the engines listed should have the partial VIN stamped either near the Engine code or above the oil filter.

CKR 73 350 Impala 175 L-48 TH 350 4-Brl Police, A.I.R.
CKR 73 350 Chevelle 175 L-48 TH 350 4-Brl Police, A.I.R.
CKR 77 350 Pontiac 170 LM-1 TH 350 4-Brl Phoenix, Ventura II
CKR 77 350 Oldsmobile 170 LM-1 TH 350 4-Brl Omega
CKR 77 350 Nova 170 LM-1 TH 350 4-Brl
CKR 77 350 Chevelle 170 LM-1 TH 350 4-Brl
CKR 77 350 Camaro 170 LM-1 TH 350 4-Brl
CKR 77 350 Buick 170 LM-1 TH 350 4-Brl Century, Regal, Skylark
CKR 70 402 Chevelle 330 LS-3 4-Spd 4-Brl

http://www.yearone.com/updatedsinglepages/Id_info/gm_engine_id/gmidimages/endinedetail1.jpg

my block off my 71 elco has VO then 3 numbers then ckr. is that the original engine?

No.

V is Flint engine plant, then month/day
ckr is 73 Nova or 77 (full line Chevrolets) 170hp a/t

Casting date probably would narrow it down.

K0325CNU
K-McKinnon industries, the GM Canada engine plant
0325-March 25th assembly date
CNU- see above app.

dangit, i thought it was! well,anyways, sbc with a 2bbl. It sure looks original and all stock