trying to decode my small block. never done it before. getting frustrated. found what i think was good info on a website which is this :
This is my opinion, and the generally accepted norm:
When people say "It's numbers matching" - what they mean is the engine (or other component, i.e the transmission) can be MATCHED to the vehicle it was originally used in. This match is done via the PARTIAL VIN stamp on the component. The partial VIN will match the vehicles VIN. If it does - it's "numbers matching", otherwise - it's not. done. end of story.
Some folks use these terms loosely, or will say "numbers correct" or something to that effect. But numbers correct is not numbers matching. Again, it either matches or it doesn't. If it doesn't match - is it correct?
Numbers matching is important when you're trying to decode a Z28 or Super Sport where the VIN won't identify the vehicle as such. You need to decode the engine and see if it matches the vehicle, and if the code signifies Z28 or SS equipment.
Lastly, in extreme cases, you'll want to verify the numbers stamped onto the component were the ones stamped into it originally and aren't restamped.
The point of this article is to help you figure out how to decode stuff.
Engine Code Stamping Numbers
All engines are stamped with an engine ID code, consisting of assembly plant code, production date and suffix code. V8 codes are stamped on a pad just forward of the right side (passenger) cylinder head
. 6 cylinder engines are stamped on the passenger side of the block behind the distributor.
Click here for Chevy Engine Code Listings
The engine date must precede the car build date, otherwise something is amiss. Some engine machining operations (decking) will obliterate the engine ID.
Engine ID Code Example: V0101CLJ
- (V = Plant, 01 = Month, 01 = Day, CLJ = Engine Suffix Code)
Another example: T0830CTY
- (T = Tonawanda, 08 = August, 30 = 30th day, CTY = 1970 396 Camaro, 375 hp, 11.0:1, TH400)
CodeEngine PlantCodeEngine Plant
FFlint (Motor)SSaginaw ServiceHHydramaticTTonawandaKSt. Catherines, OntarioVFlint (Engine)(McKinnon Industries Canada)MGM of Mexico
VIN Code Format
The vin code format is stamped onto most engines. The format consists of divisional identification number, model year, assembly plant designation and vehicle serial or sequence number.
In 68-69 model cars, the serial (VIN) number of the car the engine was installed in is stamped next to, or under the engine code ID.
Starting in 1970, the serial number
is stamped either above the oil filter
, somewhere on the block pad (in front of the cylinder head), or on the transmission
flange somewhere. Chevrolet issued technical service bulletins to indicate which engines were to recieve a vin stamp, so who knows what could have happend (or not happened).
VIN code format Example: 13N100001
(1 = Chevrolet, 3 = 1973, N = Norwood, 100001 = Production sequence of vehicle VIN)
For a list of assembly plants, click here.
On some Saginaw blocks, intakes and exhausts a "clock" was cast into the block. The clock is a circle of 10 dots, one dot for each hour of a shift (usually 10 hour shifts). An arrow points to the beginning of the shift an another dot outside the circle indicates what time of day the cast part was made. Anyways, that's what that circle thing is (if you happen to see it on something).
Small block casting date is located on driver side rear of block on flange forward of bellhousing. Big block on the right side of engine above the oil pan rails.
Casting Date Example: E038
- (E = Month, 03 = Day, 8 = Last digit of model year (1978)).
Month: A = Jan, B = Feb, C = Mar, D = Apr, E = May, F = Jun, G = July, H = Aug, I = Sep
, J = Oct, K = Nov, L = Dec
General Engine Block Specifications
While 6 different bore size blocks have been produced, the small block engine can be classified into 3 bore sizes and 3 main bearing sizes. 283 blocks (3.875" bore, 2.3" main), 302/327/350 blocks (4" bore, 2.3" or 2.45" mains), and 400 blocks (4.126", 2.65" mains). In 1968 the main bearing saddles were increased in size from 2.3" to 2.45".
CID Year Bore Main Cap
262 1975 3.671 2 bolt ONLY267 1979 - 81 3.500 2 bolt ONLY305 1976 - 96 3.736 2 bolt ONLY307 1968 - 73 3.875 2 bolt ONLY327 1968-69 4.001 (2.3" main) 2 bolt350 1968-88 4.001 (2.3" main) 2 bolt265 1994 4.001 (2.45" main) 2 bolt302 1968-69 4.001 (2.45" main) 4 bolt350 1968-96 4.001 (2.45" main) 4 bolt400 1970-72 4.126 (2.65" main) 4 bolt400 1973-80 4.126 (2.65" main) 2 bolt
Notes: 2 bolt ONLY means just that,. otherwise 2 or 4 bolt can mean either design...
Chevy Small Block - Engine Block Casting Numbers
Notes (for below):
"High Power" is the maximum rate HP this block was used for, "Low Power" is the lowest rated horsepower RPO engine the block was used in. "Main Caps" is the number of bolts holding the cap. A "two-bolt" main, or a four-bolt main. Four bolt main blocks are desirable in high performance
applications because the extra strength of the additional bolts keeps the bottom end rigid and less prone to failure. However, a properly prepared 2 bolt main engine will work just fine (often times you'll lose a rod bolt before you break a crank because it's "only" a 2 bolt main).
by using this info i have come to the conclusion that my shit is this (i think i dont even think im right anymore)
block casting number-14016379
the markings on the "pad" t0710tbc and c9f210798
block number is 14016379 which would have been made between 78-85 and it is a 350
is that all that is suppose to do is tell you the years the engines were made and what they are?
the t0710tbc ive figured out is made in tonawanda on oct, 7th and tbc which would be the engine suffix code i dont understand what that is, what does it mean?
the c9f210798 number i dont understand is that suppose to be the vin? and in which case couldnt i just do a vin look up if thats the vin?
i understand the clock one which is the time during that shift it was made vand the second dot marks which hour of that shift it was made.
i also dont understand the other markings on the engine. im going to take pictures of all the markings i have found on it. and maybe someone could explain to me what they mean im getting confused with this shit and its just frustrating me.