Chevy 400
Some, but not all, Chevy 400s have three freeze plugs per side (rear block) instead of two like other small-blocks; others have 400s have three bosses but are drilled with only two plugs (front block). Another way to tell an externally balanced Chevy 400 by its harmonic damper, which is weighted on the backside; the 350's damper is neutrally balanced.
Two- and four-bolt-main 400 blocks were produced from 1970 to 1980 with these casting numbers:
| 330817 | '72-'80 | | two-bolt |
| 3951509 | '70-'71 | | four-bolt |
| 3951509 | '74-'75 | | two-bolt |
| 3951511 | '70-'71 | | four-bolt |
Big-Block Chevy
Big-block Chevy engines are easily distinguished from small-blocks by their wide cylinder heads and splayed valves. However, telling a late 396 from an early 402 can often be very tricky because the factory used 396 blocks to produce some 402s. In that case, the way to tell is from the engine suffix code stamped on the ID pad, which is located on a deck surface ledge extending from the front of the block just ahead of the cylinder head on the passenger side. There are too many codes to print here, but the MSA-1 series and Chevrolet By The Numbers both have complete listings.These casting numbers have been used on Chevy big-blocks:
| 345014 | '74-'86 | 454 truck |
| 346236 | '74-'76 | 454 two-bolt |
| 359070 | '74-'90 | 454 truck |
| 361959 | '73-'85 | 454 |
| 3855961 | '66-'67 | 396 |
| 3855962 | '65-'66 | 396 |
| 3869942 | '66-'67 | 427 |
| 3873858 | '66 | 396 |
| 3902406 | '67 | 396 |
| 3904351 | '67 | 427 |
| 3916321 | '68 | 427 |
| 3916323 | '68 | 396 |
| 3935439 | '68-'69 | 427 |
| 3935440 | '68-'69 | 396 |
| 3955270 | '69 | 427 |
| 3955272 | '69 | 396/402 |
| 3963512 | '69-'71 | 427/454 |
| 3963513 | '73-'76 | 454 |
| 3969854 | '69-'72 | 396/402/454 |
| 3999289 | '72-'78 | 454 |
| 3999290 | '72 | 402 |
| 6272177 | '72 | 402 |
| 14015445 | '75-'87 | 454 truck |
Other Chevys
A way to quickly identify Chevy engines out of the car is by the shape of the crankshaft flange. Note: Prior to 1968, all small-blocks had a round crankshaft flange.
When searching for a small-block Chevy, beware of thin balancers, unless you're looking for a 283 or a 307. Small-block 350s and 400s have much thicker balancers.
Scalloped valve covers were used on 348s and 409s, but casting numbers are the best way to tell which is which.
From '61 to '65, 409s used casting numbers that ended in these three digits:
| Year | Block casting number |
| '61 | 723 |
| '62 | 068 |
| '63 | 814 |
| '64 | 422 |
| '65 | 656 |
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