Back when I worked in the engine shop cleaning blocks and cylinder heads was my job. I'd strip em down completly. All the freeze plugs and oil plugs. Then they would get ovened at 700 degrees overnight. afterthat I'd place the block in a shot blaster for 5 minutes and it got whacked with steel shot. never seen anything so clean in my life. for alluminum we go 500 degrees for 5 hours, then alluminum shot. Again, so very clean. it was cool.
