The LEXUS LS engines are really good and seldom fail if not suffering some mishap. IF you get a fail it is a good idea to find what the reason is if you want to keep having a reliable engine.
It cannot handle overheating or objects coming in or simmilar . If it is a loose valve seat ring or a cracked valve the best guess is that the engine has suffered an overheat episode due to water low or a zero valve clearance due to some problem or simmilar. Aluminum heads and valves overheat fast. Then at least I would hesitate to trust it after a simple repair. May work but may also fail again