plastigauge. check the main and rod bearings for clearances. can someone post the specs. is it .0025 to .003 mains / .0025 to .003 rods?
DJakken it sounds like one of your rod bearings are too tight. it could be one of the rod caps isnt the original that was on that particular rod. you can check the clearances but i'm guessing one or two of them has .000 clearance
the bad news is you have to take it apart or you will ruin it. the good news is that it will be done right
you may need to take all of the rods/ rod bolts / caps and get them checked by a machinist