Quote:
Originally Posted by Chlsnk
Looks like casting flaws to me.
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Looks like more then a casting flaw , might be a crack at the deck. I would get it mag checked at a machine shop first. Check this site for your block ID ,
http://www.nastyz28.com/sbchevy/sblock.php
Q: What is a Bowtie, or heavy duty (nickle) block and do I have one?
A: Tin and nickel are two metals that are commonly alloyed with cast iron to improve durability, hardness and heat dissipation. Some production engine blocks have the numbers "010", "020" or both cast into their front face, just above the main bearing bore. (The timing cover must be removed for these numbers to be visible.) If both numbers are present, one about the other, it indicates that the block alloy contains 10% tin and 20% nickel. A single number, either a "010" or "020" represents the amount of nickel and indicates negligible amounts of tin. No numbers, other than the casting numbers that are typically found beneath the timing cover, translates to only minor amounts of tin and nickel being present in the block alloy.
However, cylinder wall thickness is the overridering consideration - and a block with no tin or nickel and thick cylinder walls is generally preferable to a high nickel block with thin walls
http://www.nastyz28.com/sbchevy/sblock.php
Desert
PS:I have 5 of them if you need one.