Originally Posted by justacertifiedtech
When under the T-cover you will usually find 010 AND 020 this indicates metalurgy 010 = an extra 1% tin added to the metal in the block
020 = an extra 2% nickel added which makes these blocks stronger
Friendly ammendment... additional nickel makes the block harder, not stronger. Harder is great for endurance, but it can mean more resonance in high RPM applications.
Harder isn't necessarily better like everyone seems to think.
And as a sidenote, tin is added to the alloy to help it flow better into the mold.