Engine Block Casting Numbers, Date Code, Heads

[bigbrownpilot]

I’m now aware that the engine in my ‘63 is not the original engine. No big deal since it’s a driver and not a concours car. But it is a big deal as far as specifications and parts interchangeability for the engine. My block casting code is C6ME- , which should correspond to a 1966 390 passenger car engine. The date code starts with either a 5 or 6 followed by K22, which means the block was cast on October 22nd. I think the first number is a 5, so my question is would a ‘66 engine block have been cast in ‘65? I’m assuming yes, since the ‘66 models were already in showrooms. If I’m correct that make it a 315 HP 390FE with flat-top pistons and 10.5:1 compression, not a 300 HP with 9.6:1 compression.

Next is the head casting, which shows as C4AE-6090G. From what I can tell these are mild performance stock heads with a larger exhaust valve than found on a ‘63 engine. Can anyone confirm this?

All I know about the engine is that it was supposedly rebuilt sometime before 2008, and I got that from the guy who owned the car before the guy I bought it from. Would be nice to know if it’s over bored and whether the builder used hardened valve seats and did anything with the cam. It’s also using an Edelbrock aluminum manifold. i’m thinking with the manifold and Sanderson headers, maybe I’m at 325-330 HP? The engine is strong, but since the car isn’t geared for acceleration I can’t even spin the back tires on dry pavement, which is fine with me because I don’t expect a 4500# car to be a muscle car and it’s more about drivability and cruising for my wife and me. Any information on engine specs and differences based on the casting numbers I have would be appreciated!