What's the difference between long block and big block?
A long block is a complete engine, the bottom part plus the heads. A big block usually refers to a large displacement North American (muscle car) engine of around 400 cu in.
"small block" typically distinguishes between a 2 bolt and 4 bolt main. (Small block= 2 bolt main. Big/large block=4 bolt main) "long block" typically distinguishes between a rebuilt engine that has heads, rockers, rocker covers, oil pump, pan... in other words, complete, versus just block, crank, cam and pistons (short block).
The difference is in the design of the head. Also due to the head design, the physical size of the motor is larger even if CID (displacement) is identical. The best visual example I can think of is Ford 351 windsor which was a small block: http://www.mustangsteve.comW351_65.jpg and a Ford 351 Cleveland which was a big block: http://thunder-performance.com/images/Tony\'s%20351%20Cleveland%20(1).JPG Generally you can tell the difference by looking at the valve covers. if they are long, narrow…