As Barry says,
don't paint. For one thing, it doesn't help the flow of
oil to the pan. Secondly, it was mainly for sealing debris that should've been cleaned out in the first place such as casting sand and plain old dirt from inside the block. My experience is not to add anything such as paint that get loose and contaminate the
oil or worse, block an
oil gallery. So do it right the first time and remove any flash and, if you have a lot of time, smooth the lifter area with a die grinder fitted with a burr or an abrasive stone, then clean the heck out of the block afterwards.
I cover block preparation and all other aspects of engine building in my newly published book,
The Racing Engine Builder's Handbook. I show how race blocks are prepared for NASCAR Cup, Busch, late model, Dash, boat or whatever racing. Bottom line is cleanliness, it's the key. If it doesn't make horsepower, leave or get it out. The biggest problem with many engine builders is they do excessive "romancing" of the parts. Painting the interior of a block falls under this category. Save the paint for the exterior of the engine, but wash it down with brake cleaner first.
