By request we have opened the floor to discuss the suitability of the 1FZ head gasket.......Bring it on. This is my perspective. First let me state that the 1FZ engine is one of the most advanced in-line 6 cylinder gasoline engines ever offered to the public, in addition to being one of the largest displacement. The overall design and build quality of this engine is at the very top end as far as I am concerned. Limiting factors include, but are not limited to, "acceptable" gasket materials. We are dealing with an engine that is composed of an iron block and an aluminum cylinder head. The result is dis-similar metals that react to temperature changes at different rates. The challenge for the designers was to come up with gaskets that can deal effectively with the expansion rates of dis-similar metals. Before asberstos fell from grace it was a prominent feature in head gaskets for all auto manufacturers and it was very effecive. When asbestos fell from grace there was a scramble to find a suitable replacement and early "fixes" did not perform well in the long run. Toyota has, along with everyone else, changed head gasket part numbers for virtually all engines multiple times in the last several years (1FZ included) while they have searched for the best replacement. My personal read is that the great long aluminum head on the great long iron block moves around a bit with every heat cycle and that may be part of the cause. The latest version of the head gasket is visibly different than the originals and is significantly reinforced. I further believe that if asbestos was not "offed" as a bad guy we would not be having this discussion.