If you notice, not many of the third generation Chevy sixes
have problems with cracked blocks or cracked heads.
Those first and second generation Stovebolts were cast from
gray iron and were thick and was not a totally homogeneous material.
It's true that the cracks usually show up in the thinnest read
weakest, section of the block from a freeze, that just makes
sense from a structural stand point. The cracking that is
quite common in the cylinder heads are most often stress
cracks in areas of the combustion chamber where the most
stress concentration is present.
I worked as a parts man in the early 60's during the transition
from the 2nd generation to the 3rd generation sixes. The new
blocks with cast from a much more highly refined iron than
the earlier blocks were. Any one that has worked with both
engines knows how much lighter the later blocks are. Ford had
been using the process for some years in their V8's before
GM adopted it. If my memory serves me right the technology
was compacted graphite cast iron which is lighter and
stronger than gray cast iron, making the alloy a more
attractive alternative to the latter in the production
of cylinder blocks.
dg
Last edited by Denny Graham; 10/26/2015 11:32 AM.
