My big bore 426 (444) developed a head gasket leak between the cylinder and water jacket. I pulled the head and replaced the head gasket...pretty straight forward. When I started it, the engine clattered like a mofo. It was not noisy like this before I took the head off. I really couldn't tell where the noise was coming from. I pulled the valve cover and rechecked the cam timing, thinking that I had dorked it up and had valves kissing the piston. Yes, it was that loud. Nope, timing was good. I took of the wet side cover and checked the primary drive gear and the clutch. All good. I checked the valve clearances. Both exhausts were at .008, the two outside intakes were at .004, and the center intake was at .005. All within spec. I pulled off the cam caps to look for any evidence of partial siezure. All good, and yes, the half moon clips were in place. By the way, the bike has HotCams intake and autodecomp exhaust cams. Retorqued the cam cap bolts to 95 in-lb. Put it all back together, and still clatters like a mofo. I pulled the head off again. No valve marks on the piston and no piston marks on the valves. I pulled all of the valves anyway and checked the stems. Nothing bent. I pulled the flywheel and stator and looked at the cam gear on the crank. Looks good. The cam chain guides are in good shape. Put it all back together again, and still clatters. I replace dthe cam chain tensioner with a spare that I had in the garage. No difference. The bike didn't make this noise before I pulled the head, so I'm sure I put something together wrong. The only new parts are the head gasket and head bolts, and now a timing chain tensioner, so I doubt that it's a parts issue. Anyone have any ideas?