I was reviewing the pictures of the 455 I swapped into my cutlass after becoming educated here. I noticed the exhaust valves on the inside cylinders of one of the heads have a distinct cone-shaped depression (head on the left side of attached picture), while the rest have a domed depression. Does anyone know what the difference is and if there is any significance. The heads appear to have some wear, but I don't notice any problem with the way the car runs. Just curious.

 

Different brand valves. Different aftermarket manufacturers do them differently. The ones with the smoother depression might be a performance valve but the only way to know is to pull it out and see if there is a number on it up near the top of the stem.