Originally Posted by chevypower1
the 455 is a much better engine that the 400 and the 421. You should be happy with it.
I've been running Pontiacs for almost fifty years and I've had all sizes. The 455 is no better than the 421/428 or 400. As a matter of fact, the 400 block is stronger because of it has 3 inch mains vs the 3.25" mains of the 421/428 and 455. I know because I've had one start to split. For the horsepower needed for a healthy street engine, the 455 would be the best choice because it has plenty of torque without replacing any internal components, even though I would change to forged rods and pistons.