What is this motor

[sean1969c10]

I see no reason to be afraid of a 1 pc rear main seal block for a street or street and strip application. They have a lot of thing going for them : better gasket sealing surfaces, many have factory roller cam, 1 pc rear main seal, and just better machine work from GM. If you start making more than 500hp you really need to start thinking about an aftermarket block, just to protect your investment in parts. I can't imagine sleeving 8 holes in a block unless it was numbers matching for something very valuable. At the shop where I work we charge 175.00 per hole to sleeve a cylnder. It is a lot of work to do it right, I have seen many blocks that were sleeved where the sleeve moved causing the engine to have head gasket problems or consume oil and ultimately have to have the block replaced. I have seen some blocks go .080, I wouldn't want it. I have also have had a 3970010 block bored .060 in my Nova window a cylnder at 6500 rpm. I found chunks of cylnder that were under .050 thick. My advise is to have a block sonic checked before going .060. Just my .02c