There are plenty of instances where perfectly good—and often rare—cast iron cylinder head and engine block castings are scrapped due to the presence of a hairline crack in an external surface.

Porting GM's Iron Vortec Heads Potential Can Be Unlocked From Stock Heads By Using A Set Of Long Cast-Iron Vortec Heads As An Example Staff WriterWriterMay 02, 2003 See 1 Photo ...