when the engine is timed correctly pistons one is NOT at TDC, by the sounds of it the cams are 180 deg out as the plate should slide in easy, turn the engine over so they line up and check the pointer on the clutch through the hole in the top off the bell housing or with the mark on the crank pulley and block ..... there is a guide in the premium members section on how to time the VR6 engine correctly