Fortunately, the Cadillac block had no cracks, but this six-cylinder
Chevrolet block wasn’t as lucky. After it went through the
magnaflux process, this crack became clear.Inspection time
With the engine block cleaned, it’s nearly ready to expose all of its
imperfections. At this point, Herman makes a visual inspection, looking
for obvious signs of cracks. He also examines the cylinder walls for
grooves and scoring. This engine has a significant groove in one cylinder
wall, and shallow scoring in at least three other cylinder walls. As is
typical of an engine with many miles, there is also a ridge at the top of
each cylinder wall. This ridge represents the small area that the piston
does not reach during its throw, so its height remains at or near the
original location of the cylinder wall. The large area below the ridge is
lower, caused by years and miles of the piston passing over the cylinder
wall.
Before Herman develops a plan of attack to machine or re-sleeve the
cylinder walls, it must be magnafluxed to identify small cracks that are
not visible to the eye. If there are significant cracks in the block, or
many small cracks, the block may not be worth rebuilding.
To magnaflux the block, an atomizer is used to spray red magnetic
powder on the deck where the cylinder heads are fastened, the front and