Casting numbers are by far the best way to I.D. a block, this number is raised about an 1/8 of an inch and is very easy to spot. The engine I.D. number stamped into the front of the block on a milled pad is not a reliable way to I.D. and engine because they are so easily faked. One way to use these milled surfaces though it to help identify the approximate time the block was cast. Late model engines have the smallest pad,measuring about an inch and three quarters. Engines built in the 50's have a pad about three and an eighth inches and engines built in the 60's and 70's use a pad about four and three eighths inches.
The design of the small block Chevy has remained virtually unchanged since it was first built. The very first small blocks from 1955-57 featured a front engine mounting system. They were changed to the sides for the 1958 model year. If the small block your trying to identify doesn't have threaded mounting holes on the side of the block then it's a pre 1958 block. In 1967 there are two threaded holes on the drivers side of the block right above the oil filter boss for the clutch counter shaft to mount to. What's called a "Road Draft Tube" was designed into the block in 1963 to help ventilate the crankcase. The PCV system has since been redesigned twice to what we see in the small block today. The Hole at the top rear of the lifter valley was machined into the block from 63 to 68. In the spring of 68 the 302,327 and 350 Chevy's came with a large journal crank to help increase strength and durability in the higher horsepower engines. 1969 marked the year that four bolt main blocks came out. at this time the horsepower numbers really demanded higher strength bottom ends. The one peice rear main seal was designed into the block and available in 1995-96. The engine also featured a reverse flow water pump that was designed to cool the cylinder heads first,this also helped keep the air fuel mixture cooler and increased horsepower while at the same time kept the operating tempurature of the engine lower for even more increased efficiency.
Found only on the small blocks installed in the Chevy II, A points out the dipstick tube provision is blocked off and B points out that the front clutch counter shaft hole is not machined out. The dipstick tube was re-located to the front of the oil pan on the drivers side due to restrictive space under the hood. Note that these blocks also had a recessed oil filter boss to clear the front cross member. 
Here is a very good description of the casting number,shown here is the "010" block. This block is the highest nickle content small block built by Chevy, the 4 bolt main blocks can be safely bored 040 without core shift becoming a problem. These blocks were cast and installed from 1969 to 1979
Small Block Chevy Basic specification
Disp Bore Stroke Production Years
262 3.67 3.20 1975
265 3.75 3.00 1955-56
267 3.50 3.48 1979-82
283 3.87 3.00 1957-67
302 4.00 3.00 1967-60
307 3.87 3.25 1968-73
327 4.00 3.25 1967-69
350 4.00 3.48 1967-98,still produced for aftermarket and marine.
400 4.12 3.75 1970-76
| Casting | CID | Year | Model Aplication | Comments |
|---|---|---|---|---|
| 330817 | 400 | 73-76 | Passenger | 2 bolt main,3 freeze plugs/side |
| 330817 | 400 | 75-80 | Truck | 2 bolt main,3 freeze plugs/side |
| 355909 | 305 | 76-79 | Truck | |
| 355909 | 305 | 78-79 | Pass,Camaro,Malibu,Monte Carlo,Nova | |
| 360851 | 262 | 75-76 | Monza | |
| 361979 | 305 | 76-79 | Truck | |
| 361979 | 305 | 76-79 | Pass,Camaro,Malibu,Monte Carlo,Nova,Chevelle | |
| 366245 | 350 | 78-79 | Pass,Malibu,Camaro,Nova | Dipstick in oil pan |
| 460776 | 305 | 76-79 | Truck | |
| 460776 | 305 | 78-79 | Pass,Malibu,Camaro,Nova,Monte Carlo | |
| 460777 | 305 | 78-79 | Pass,Malibu,Camaro,Nova,Monte Carlo | |
| 460778 | 305 | 78-79 | Pass,Malibu,Camaro,Nova,Monte Carlo | |
| 471511 | 267 | 79-82 | Malibu,Monte Carlo | |
| 3703524 | 265 | 55 | Corvette | 195 HP,no oil filter |
| 3703524 | 265 | 55 | Passenger | No oil Filter provision |
| 3720991 | 265 | 56 | Corvette | with no oil filter |
| 3720991 | 265 | 56-57 | Truck,Pass | with no oil filter |
| 3731548 | 283 | 57 | Corvette,pass,truck | no side motor mounts |
| 3737739 | 283 | 58-59 | Corvette | Early 1959 |
| 3737739 | 283 | 58-61 | Passenger | |
| 3756519 | 283 | 58-61 | Corvette | |
| 3756519 | 283 | 58-62 | Passenger,Truck | |
| 3782870 | 327 | 62-65 | Corvette | Sm journal |
| 3782870 | 327 | 62-65 | Passenger,Chevelle,Truck | Sm journal |
| 3789817 | 327 | 62-65 | Passenger,Chevelle,Truck | Sm journal |
| 3789935 | 283 | 61 | Corvette | Late 1961 |
| 3789935 | 283 | 62-64 | Truck | |
| 3789935 | 283 | 63-64 | Passenger,Chevelle | |
| 3790721 | 283 | 64-65 | Chevy II | Recessed oil filter boss |
| 3791362 | 327 | 65-67 | Chevy II/Nova | Recessed oil filter boss sm journal |
| 3794226 | 283 | 58-62 | Truck | |
| 3794460 | 327 | 68-69 | Pass,Chevelle,Camaro,Nova | Large journal |
| 3837739 | 283 | 58-62 | Truck | |
| 3849852 | 283 | 58-63 | Passenger | |
| 3849852 | 283 | 58-67 | Truck | |
| 3849852 | 283 | 64-67 | Passenger,Chevelle | |
| 3849935 | 283 | 62-67 | Passenger,Chevelle | |
| 3858174 | 327 | 64-67 | Passenger,Chevelle,Camaro | Sm journal |
| 3858174 | 327 | 64-67 | Truck | Sm journal |
| 3858174 | 327 | 66 | Corvette | 300,350 HP Sm journal |
| 3858174 | 350 | 67 | Camaro | |
| 3858180 | 327 | 64-67 | Pass,Chevelle,Camaro | Sm journal |
| 3858180 | 327 | 64-67 | Truck | Sm journal |
| 3858180 | 327 | 65 | Corvette | |
| 3862194 | 283 | 66-67 | Chevy II | Recessed oil filter boss |
| 3864812 | 283 | 63-64 | Pass,Chevelle,Truck | |
| 3889935 | 283 | 63 | Truck | |
| 3892657 | 327 | 64-67 | Pass,Chevelle | Std & Hi Perf sm journal |
| 3892657 | 327 | 64-67 | Truck | sm journal |
| 3892657 | 327 | 66-67 | Corvette | 300,350 HP sm journal 2 bolt main |
| 3892657 | 302,327 | 67 | Camaro & z28 | sm journal 2 bolt main |
| 3896948 | 283 | 65-67 | Pass,Chevelle,Truck | |
| 3903352 | 327 | 64-67 | Pass,Chevelle,Camaro | sm journal |
| 3914635 | 307 | 68-73 | Pass,Chevelle,Camro, Nova,Truck | |
| 3914636 | 307 | 68-73 | Pass,Chevelle,Camro, Nova,Truck | |
| 3914660 | 327 | 68-69 | Pass,Chevelle,Camro, Nova,Truck | |
| 3914678 | 302,327,350 | 68 | Camaro,Z28 | large journal,2 bolt main |
| 3914678 | 327 | 68 | Corvette | 300,350 HP lrg journal 2 bolt main |
| 3914678 | 327 | 68-69 | Pass,Chevelle,Camaro, Nova,Truck | |
| 3914678 | 350 | 68-74 | Pass,Chevelle,Camaro, Nova,Monte Carlo | |
| 3914678 | 350 | 69-76 | Truck | |
| 3914678 | 350 | 78-79 | Pass,Malibu,Camaro ,Nova | |
| 3932371 | 307 | 68-73 | Pass,Chjevelle,Camaro, Nova | |
| 3932371 | 307 | 69-73 | Truck | |
| 3932373 | 307 | 69-73 | Pass,Chevelle,Camaro, Nova,Truck | |
| 3932386 | 327 | 68-69 | Pass,Chevelle,Camro, Nova | Large Journal |
| 3932386 | 350 | 69 | Corvette | 300,350 HP |
| 3932386 | 350 | 69-74 | Pass,Chevelle, Camaro,Nova,Monte | HI perf,4 bolt main |
| 3932388 | 350 | 68-74 | Pass,Chevelle, Camaro,Nova,Monte | 2 bolt main |
| 3932388 | 350 | 69-76 | Truck | 2 bolt main |
| 3932442 | 350 | 67 | Camaro | |
| 3933180 | 327 | 68-69 | Pass,Chevelle,Camaro, Nova,Truck | Large Jounal |
| 3941174 | 307 | 68 | Truck | |
| 3951509 | 400 | 73-76 | Passenger | 2 bolt main, 2 freeze plugs/side |
| 3951509 | 400 | 75-80 | Truck | 2 bolt main, 2 freeze plugs/side |
| Casting # | CID | Year | Model Application | Comments |
|---|---|---|---|---|
| 3951511 | 400 | 70-73 | Pass,Chevelle,Monte | 4 bolt main, 3 freeze plugs/side |
| 3951511 | 400 | 75-80 | Truck | 4 bolt main, 3 freeze plugs/side |
| 3955618 | 327 | 68-69 | Pass,Chevelle, Camaro,Nova | Large Journal |
| 3955618 | 302 | 69 | Camaro,Z28 | early 69,4 bolt main |
| 3955618 | 350 | 69 | Corvette | 300,350 HP,4 bolt main |
| 3955618 | 350 | 69-74 | Pass,Chevelle,Camaro,Nova,Monte Carlo | |
| 3955618 | 350 | 69-76 | Truck | |
| 3956632 | 307 | 69-73 | Pass,Chevelle,Camaro,Nova,Truck | |
| 3970010 | 350 | 69 | Corvette | late 69,4 bolt main |
| 3970010 | 302 | 69 | Camaro | Z/28,Late 69, 4 bolt main |
| 3970010 | 350 | 69-79 | Truck | 2&4 bolt main |
| 3970010 | 350 | 69-79 | Pass,Chevelle,Camaro,Nova,Monte Carlo | 2&4 bolt main |
| 3970010 | 350 | 70 | Corvette | 300,350,370 HP 4 bolt main |
| 3970010 | 350 | 71 | Corvette | 270,330 HP 4 bolt main |
| 3970010 | 350 | 72 | Corvette | 200,255 HP 4 bolt main |
| 3970014 | 350 | 69-77 | Pass,Chevelle,Camaro, Nova,Monte Carlo | 2 or 4 bolt main |
| 3970014 | 350 | 69-79 | Truck | 2 or 4 bolt main |
| 3970014 | 350 | 72 | Corvette | late '72,200 HP,255 HP 4 bolt main |
| 3970020 | 307 | 68-73 | Pass,Chevelle,Camro, Nova | |
| 3970020 | 307 | 69-73 | Truck | |
| 3970024 | 307 | 69-73 | Pass,Chevelle,Camro, Nova,Truck | |
| 3992386 | 327 | 68-69 | Pass,Chevelle,Camro, Nova,Truck | Large Jounal |
| 14010201 | 305 | 80-85 | Pass,Malibu,Monte, Camaro,Nova,Truck | |
| 14010202 | 305 | 80-85 | Pass,Malibu,Monte, Camaro,Nova,Truck | |
| 14010203 | 305 | 80-85 | Pass,Malibu,Monte, Camaro,Nova,Truck | |
| 14010205 | 267 | 80-82 | Malibu,Monte Carlo | |
| 14010207 | 350 | 80-85 | Pass,Malibu,Camaro | |
| 14010207 | 350 | 80-81 | Truck | Light Duty |
| 14010209 | 350 | 80-81 | Pass,Malibu,Camaro | |
| 14010209 | 350 | 80-85 | Truck | Heavy Duty |
| 14010280 | 267 | 80-82 | Malibu,Monte Carlo | |
| 14016376 | 267 | 80-82 | Malibu,Monte Carlo | |
| 14016379 | 350 | 77-79 | Pass,Chevelle,Camaro, Nova,Monte | |
| 14016381 | 305 | 76-85 | Truck | |
| 14016381 | 305 | 78-85 | Pass,Malibu, Camaro,Nova | |
| 14016383 | 305 | 80-85 | Truck | |
| 14088526 | 350 | 87 | Camaro | |
| 14088548 | 350 | 86-88 | Truck | One Piece rear main seal |
| 14088551 | 305 | 86-88 | Truck | One Piece rear main seal |
| 14088551 | 305 | 86-88 | Pass,Malibu | One Piece rear main seal |
| 14093627 | 305 | 87 | Pass,Malibu | One Piece rear main seal |
| 14093638 | 350 | 86-87 | Truck | One Piece rear main seal |
| 14093638 | 350 | 87 | Camaro | One Piece rear main seal |
| 14101148 | 350 | 87 | Camaro | One Piece rear main seal |
| 14102058 | 305 | 87 | Truck | One Piece rear main seal |
| 14102058 | 305 | 87 | Pass,Malibu,Monte Carlo, Camaro | One Piece rear main seal |
| 14316379 | 350 | 69-85 | Truck | Two Piece Rear Main Seal |
| 14316379 | 350 | 78-81 | Pass,Malibu, Camaro,Nova | One Piece Rear Main Seal |
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