I purchased a '93 Range Rover CLWB in December which had a blown head gasket. After reading on-line about the engine (of course after I purchased the vehicle) I determined it would probably be better to just buy a replacement engine so I obtained a used 4.2 and am currently rebuilding it before installing it. This is the first time I have done anything like this and had a few questions. I removed the cylinder heads, had a valve job and a 40 thousands grind done on them (thank-you for that information PT Schram) since I am replacing my head gaskets with the updated composite style gasket. A friend of mine, who is a mechanic, asked what I was doing about the lower end (main bearings and piston rings specifically) after having the heads redone because I might get some "blow-by"? What exactly does this mean and how badly will it effect the engine once it is put back together if I do indeed have "blow-by"? I purchased this vehicle for only $400 and thought I would be able to finish it fairly inexpensively but things are definitely adding up (head gaskets, new head bolts, new radiator hoses, new belts, new valley pan gaskets, new rocker cover gaskets, new oil pan gasket, and new transmission filter/gasket set...to mention a few). Can anyone explain this to me better and give me some advice? Thank-you