Small Block Blocks Identification :: 1964 - 1990

Small Block Blocks 1964 - 1990

Small Block Identification

• A small block measures 12" between the heads at the manifold base.
• Facing the front of the engine, at the top surface of the timing chain area, to the left of the oil fill tube, there is a code about 1.5" high followed by the casting number. A letter indicates a big block, a number indicates a small block.
• Big blocks have a little hump in that area, whereas the small blocks have a completely flat shelf.
• Small blocks from 1977 onward will have the CID or liters cast in large numbers right above the center core plug. The engine VIN number will also be cast onto the side of the block.

From the outside they don't look different at all because the 260, 307, 330, 350, and 403 are all the same basic block. But externally the distributor, valve covers, water pump, front cover, oil pan, carb, etc are the same.

[ Thanks to Chris Witt, Tony Waldner for this information ]

ID/                    Casting
Code   Year(s)   CID   Number    Notes
1      '64       330   381917
2      '65       330   381917
2      '68-70    350   395558
3                330
4
5
       '73,'74   350   395558
2A     '76-81    260             Solid main webs for 2A's only? At least for '76.
2B     ??-'81    260   557751    Windowed main webs. Windowed main webs for 2B's only?
3A
4A     '77       403   557265    Solid main webs possibly
                       553990    for these three
                       554990    casting numbers.
4B     '77-'79   403   557265    Windowed main webs always.
??     '85       307   556607
5A     '81-      307   3161
D3               350   7582      Diesel

Please refer to the Engines section as well!