I recently acquired a 400 and was told it was a marine block due to an "X" cast on the block on the front left side of the motor, right below where the i.d. boss is. Its a '77 block with 452 heads and a cast iron intake stamped '78. Now I was told by the guy I got it from that because it had an "X" cast on it, it meant it was a marine block and therefore has a steel forged crank in it. Can anyone confirm this or is there a way to tell by looking at the crank because it's on a stand with no pan and hasn't had oil ran through it since he "redid" it. Any help would be appreciated as I'm looking to sell it and don't want to mislead anyone. Thank you.

 

A steal crank should have a damper that does not have a counter weight on it .