Just in order to avoid confusion, also considering that the above photos are labelled as "Man 800 hp Engines head & valve": Actually, that's not what they are. In fact, they are related to the 900 hp version instead, which was a pretty substantial redesign of the V8 block, used by MAN as a sort of testbed for the transition to common rail. And among several other modifications, with that engine, they also introduced 4 valves heads. Before it, all MANs, including those previously mentioned in this thread, had plain vanilla 2 valves which (AFAIK - touch wood!) very rarely must be replaced/reseated.
My MAN story, bear with me; I was already doing light maintenance on a seasonally passing Viking Princess with mechanical V12s many (many) moons ago. I was impressed with these engines, not the boat. A favorite customer then purchased a boat with CR900s and found nobody around that could work (well) on them. Like a (dr**&^^%unk) kid, I stepped up to the plate. Quickly finding support in Webster Texas, I went to work. Damm these are great engines. Finally found (many miles aweigh) a MAN kid for our heavy work. Many (many) years later, I still luv the engines, sadly nobody worth my spit in these swamps to work (well) on them still. I still pass any heavy MAN calls to that far aweigh kid. If I was just a lil younger with out my back issues, I would be pursuing that local MAN service trade. What is the first thing I tell anybody about purchasing a MAN powered boat?? Find a great shop to support you.. If not, shop for another boat. Ben, Seems like you found a good tech that understands some MAN values. Possibly sending the heads to my same same Texas shop. As a good friend explained to me a while ago; BOAT Bend Over And Take-it But ya know, we luv our boats. Like a wife, we luv the abuse,, spilled blood,, correct language,, blown check book,, ... Happy and safe new year Ben and to all that tolerates me..