kobelco sk 200 overheating

got sent to look at said exc. Had been overheating. has a 6bt cummins in it with 8000 hrs. when I checked it out the radiator was pretty plugged up looking so I pulled radiator, had it cleaned and rodded, put in a t-stat (didn't have one), and threw in a new waterpump for good measure. still overheated. figured it had to be a head gasket. pulled head and sure enough it was warped .015 and had a crack. yesterday I put it back together and it still overheated. when I say overheat, I mean climbing to 220 in under 10 minutes and would keep going it I didn't stop machine. put in my mechanical gauge and sending unit to be sure and It read the same. I pulled the t-stat out and unhooked the radiator hoses from the rad. and poured a bucket of water into the bottom rad. hose (suction side). I could pour water in way faster than the water pump could pump it through the engine and I wasn't getting water out of the top hose with very much flow. just for kicks I put the old water pump in just to make sure the new pump wasn't a dud. same result. I thought maybe the belt got routed wrong and the waterpump was running backwards but I could only get the belt on one way, which turns the waterpump counter clockwise. the only thing I can think of now is that I have a blockage in the engine. does anybody have any other ideas before I pull the engine and start disassembling?