I have a 1640 combine and last year I went from a 4 row wide to a 6 row narrow corn head. It has fiberglass snouts so it should not be as heavy as steel. There are times that it will not raise high enough to lock the head up. It only lacks about 1/2 inch from being able to lock. The book shows it should handle the head and it raises and lowers just fine. So do I have a pump problem or something else?