I like assembling a motor myself because then I know things about it. I know things like the oil galley plugs are not set to deep, blocking off some very important oil passages, I know that my ring gaps are set to .030" on top, .018-.020" on the second and oil rings. I know my bore is 4.0215" for a piston to wall clearance of .0015." I know me deck is not square and therefore is not exactly .015" but ranges from .008 to .0015." I know I have a cast steel crank 2442 that is turned .020" under. I know that main bearing clearances are .002" for 1-4 and .0025" for #5. I know my rod bearing clearances are all .0019." I know my lifter bores are not loose and neither are the distributor to oil galley seals. I know the exhaust valve seats on the stock Vortec heads were cut too wide and that the springs are not letting me see the full potential of my cam (they will be replaced shortly). I know that I have a high pressure, stock volume oil pump. I know I have a helicoil holding in my #5 main bearing. These are all reasons I like to assemble my own engines. I know everything about it now. I know what it can do and I know it's limitations. Also, since my time is cheap to me, I can afford to do things like smooth out sharp edges in the combustion chamber.