mechanical fan with schroud...no blockage. Now....IF the engine is working harder at high speed, it may be generating too much heat for the Alum rad I have in now. The motor has a nice cam/stroked and stock bore. It's also a waterblock. It's got to be the hose or rad and the hose is easier and cheaper to try.Thanks to all. (the coolant is newer and 50/50)(stat is not a player unless not opening and it opens)