Fig. 42.8
The type of cast-iron alloy the block is made of is sometimes a good thing to know for a durable block. Behind the timing cover on the front of the block you can find out what alloys have been added to the cast-iron. What you are looking for is 010s and 020s. A 010 over a 020 See Fig.42.8 indicates a block produced with a cast-iron alloy having 1 percent tin and 2 percent nickel.
The tin helps in the pouring of the block and makes the cast-iron more ductile. Because the tin helps casting the block there is less problem with hot spots caused by porous metal.
The nickel used in the block does two things, it refines grain structure of the cast-iron, increasing its strength and work-hardening characteristic. As the rings rub up and down the cylinder walls it tends to harden the surface extending bore life.
If the block has only one number, either a 010 or 020 this means it contains no deliberately added tin and has either 1 or 2 percent of nickel added. If no number is present then no additional nickel or tin has been added to the cast-iron.