How to ID a Small Block Engine Block:

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krazykuda

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How to ID a SB Engine Block:

Many people ask how do I find out what a small block engine is? You can find out alot about it if you know where to look....


The first question is: "How do I know what size it is?" That can be easily found out by looking at the driver's side of the block (the one without the oil filter). The casting number is found on the driver's side (left side) of the block as shown here:


View attachment 1714943099

Here is a close up of the casting number. You can see that the engine size is cast into the block at the end of the casting number. This is one for a 360:

View attachment 1714943100

Now you want to go to the passenger side (right side) of the block where the oil filter mounting pad is for more juicy info. Here is what you are looking for in the picture.

A. This is the VIN pad. This is where the last 8 digits for the vehicle's VIN number that is usually found on the dash board. You can decipher what model year vehicle the engine came in, and the assembly plant that the vehicle was made in. The last 6 digits are the sequence number from the VIN found on the dash board. This number needs to match the last 8 digits of your VIN plate on the dash to be a "Numbers Matching" engine for your car:

B. This is the casting date for the block with the clock to show what time it was cast.

C. This is the shift that the block was cast on at the casting factory, D is for day shift, N is for night shift:


View attachment 1714943101

Here is a close up of the casting date and shift on the side of the block:

View attachment 1714943102

Here is a close up of the VIN pad. This is where the last 8 digits for the VIN number for the vehicle that it came from the factory. The first digit is the model year that the vehicle that the engine originally came in. The second digit will tell you what vehicle assembly plant built the vehicle. The last 6 digits are the sequence number for the VIN. These can be hard to see as they get covered with paint, grease, and grime, so you may need to do some scraping to find it and read it:

View attachment 1714943103

Here's a chart to decode the whole vehicle VIN number:

View attachment 1714943104

On the front of the block under the driver's side (left side) head, you will find another batch of numbers stamped into the block. This is the information from the engine assembly plant. Like the VIN pad above, it can be covered in paint, grease, and grime; so you may have to do some scraping and cleaning to see it.

View attachment 1714943105

Here's a close up of where you will find the information:

View attachment 1714943106

Here's the chart to decode the engine plant information:

View attachment 1714943107

Good luck and have fun!



Here's some additional info that Rocky_JS added to help us:

Some additional stuff I have saved. These are the special engine assembly codes.

T = Truck
R = Regular Fuel
P = Premium Fuel
LC = Low Compression
HC = High Compression
MP = Maximum Performance
HP, HP2 = High Performance, HP2 = 2nd shift
X = .001" Undersize Crank
X = .U10" Undersize Crank
Diamond = .008" Oversize Tappets
OS = .005" Oversized Valve Guides
X = Oversize Valve Guides
S = Special Engine (possibly warranty)
SP = Special Engine TA340 or police and seen on big block a-body engine also
WT = Water Tested
H = Hemi before displacement ex. H426
A = .02U" Oversize Cylinder Bore
B = .010" Undersize Main and Rod Bearings
E = Cast Crank
H = Standard 4-bbl V8

With some of the over/undersized components you may see a 4 or 4I or 4E. These will equate to cyl number 4 and/or 4 Intake or Exhaust. Sometimes not noted at all as to which cyl has oversized lifter etc.

Model Year
the following is a list of letter codes and their corresponding years. The year always precedes the engine displacement. Ex: C273 = 1967 273 engine.
P = 1960
R = 1961
S = 1962
T = 1963
V = 1964
A = 1965
B = 1966
C = 1967
D = 1968
E = 1969
F = 1970
G = 1971
H = 1972
J = 1973
K or 4 = 1974
L or 5 = 1975
M or 6 = 1976
N or 7 = 1977

Engine Assembly Plant Codes
K = Toluca
M or PM = Mound Rd.
MV or MN = Marysville
T or PT = Trenton
W = Windsor

Read more about this article here...
 
Last edited:
pre 68 I think the pan rail stamping is not implemented yet. Good stuff. Every block that I had has been a night shift! Was this a 24 hour line~ maybe there are 2 night shifts and one day?
 
It also has been added to the "How To" section.

Thanks everyone!
 
FYI: You can save the chart pictures to your hard drive and then open them in a picture viewing software to zoom in on them to read them better.
 
Some additional stuff I have saved. These are the special engine assembly codes.

T = Truck
R = Regular Fuel
P = Premium Fuel
LC = Low Compression
HC = High Compression
MP = Maximum Performance
HP, HP2 = High Performance, HP2 = 2nd shift
X = .001" Undersize Crank
X = .U10" Undersize Crank
Diamond = .008" Oversize Tappets
OS = .005" Oversized Valve Guides
X = Oversize Valve Guides
S = Special Engine (possibly warranty)
SP = Special Engine TA340 or police and seen on big block a-body engine also
WT = Water Tested
H = Hemi before displacement ex. H426
A = .02U" Oversize Cylinder Bore
B = .010" Undersize Main and Rod Bearings
E = Cast Crank
H = Standard 4-bbl V8


Thanks for the info. :prayer:
 
Karl,
I'll have to keep a few of these in mind when I go to my Step-Sons neighbors "junk yard" again. this was a great thread to teach, I even learned something. imagine that!? LOL
 
pre 68 I think the pan rail stamping is not implemented yet. Good stuff. Every block that I had has been a night shift! Was this a 24 hour line~ maybe there are 2 night shifts and one day?

No rail pad? The. Where to look?
 
Rumble on 67 and earlier it has all the same info except the pan rail vin all other identifiers are the same. You should look on the left front of block under the head mounting.
 
Thanks guys. I've done a lot more bodywork than engine and decoding stuff. Very helpful. :) :) :)
 
Thankyou for all the decoding info.Very helpfull,my son and I just finished a GMC 5.7 VORTEC engine rebuild,so this kind of info.is good'I hope our 273 commando isnt quite so PICKY as that VORTEC was.Thanks again.
 
Thanks for this info! I just spent 3 hours looking for engine assembly information. I am thankful someone took the time to do this and just want them to know, it is still helping people.
 
I read through this post and don't seem to be able to desipher what is in my car.
On the right side (oil filter) it has te shift (N) by my guess and 2-18-66. I was told the history that the car is maybe the last one off the line 7/31/66. I'll research more on that later.

On the left side I only seem to have 2806080-1

In the next couple of days I'll dig around and see if I can find the front side numbers and any other ID to confirm what I'm hoping is the original 273 Commando.


100_1394.jpg


100_1395.jpg
 
Last edited by a moderator:
I read through this post and don't seem to be able to desipher what is in my car.
On the right side (oil filter) it has te shift (N) by my guess and 2-18-66. I was told the history that the car is maybe the last one off the line 7/31/66. I'll research more on that later.

On the left side I only seem to have 2806080-1

In the next couple of days I'll dig around and see if I can find the front side numbers and any other ID to confirm what I'm hoping is the original 273 Commando.


The early 273's did not get the VIN number stamped on the block, therefore it makes it impossible to tell which car it originally came in....

Your engine block may or may not have been "the last one off the line", but there are no guarantees without more documentation. If the engine was first time through, then it wasn't for sure, but if it was recycled or put in a bank of engines, then it could have, like I said, there is no way to tell for sure without more documentation....
 
but is this a 273?
want to verify before ordering a complete gasket set, she shows signs of never being cleaned of 50 years of grime. Ran pretty good, no unusual noises. Going to degrease and clean, replace all gaskets, pint and put her back in with new clutch and cleaned 4 sp.
 
thank YOU !!!!!!!!!! numbers matching block !!
 
great info I am a lifelong transmission rebuilder
starting a resto on my sons 75 duster, original 360 auto, sunroof, fold down seats buckets.
the trans is original numbers matching unit, the motor is not. its a 360 casting 4006830-360-3
all thats on front pad is R7
thoughts?
going to pull it next week to send off to machine shop just like to know where We are starting
20220621_201749.jpg
 
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