Quote: I am not trying to turn this into a 400/451/??? combo post.
I was afraid that was going to happen. Just kidding. I'm sure some other "experts" will chime in later. I'm not an expert, but I do have some data that may help your decision.
From the Mopar Engines Manual: The 1976-1977-1978 blocks for the 400 and the 440 are a thinwall casting design. As such they shouldn't be overbored more than .020".
Now most people will say that the only true way to tell is to have your block sonic tested, before you build it. I’m just giving you the info that I have.
As far as other factors for your decision, cost is not one of them. It will cost you roughly the same amount of money to build either the 431 or the 451. The only difference is the cost of the Piston and Rings, but that may not be enough to worry about. The weight of the Rotating Assembly would be slightly different, but is it enough to make the decision? Then is comes down to cubes, 20 more at 1hp per cubic inch is 20HP. It is just an example guys, so don't tell me that it will make more or less than 1hp per in3. It is an example.
