Scrap block wanted please

[Alan]

Unless you are doing something really special, the ports are too big already. All you need to do is remove the sharp edges and maybe straighten out the curve on the sides of the inlet ports. Don't worry about going through to the water jacket - you won't unless you've removed way too much metal. What I always do is get the cylinders bored first, because that is where you may get a problem and it's better to find out before you've invested several hours with a rotary file.