5. Magnafluxing - Magnaflux is actually a brand name of the Illinois Tool Works, and is one of several types of Magnetic Particle Inspection (MPI) systems, but it is so widely used that “magnafluxing” has become the slang term for the process. To locate cracks too fine to be detected with the naked eye, you can expose the block to a strong magnetic field and apply a ferrous metal dust. The dust is attracted to the pole ends of a magnet, so if a crack exists, the dust will gather around it. This is one of the most critical steps on a vintage block since hairline cracks are common. The key thing here is to identify an unusable block before additional operations are performed.