For some reason "400 Uniblock" doesn't sound right. But that's basically what it is.
According to Motortrend/Hot Rod
While Buick offered small-block and big-block designs that shared little, Pontiac by contrast built all its V-8 engines from the same basic architecture. Pontiac never added a "big-block" engine family in the late 1950s or early 1960s like others did but rather increased the size of its existing OHV V-8 design. All Pontiac engines between 326ci and 455ci have the same external dimensions, with only internal alterations to bore and stroke. All had the same 6.665-inch connecting rod, and the Pontiac 350ci "small-block" of 1968 was derived from the earlier 389ci V-8, but with a smaller 3.87-inch bore (versus the 389's 4.06-inch bore).
When looking at the cost-versus-power problem through
Pontiac glasses, it clearly pays to go big since the cost to build any Pontiac V-8 is essentially the same. Pontiac fans should note that at around the 600hp mark, Pontiac blocks develop a tendency to crack down the valley and require additional measures to provide reliable support in this fatigue-prone area. Pontiac engine builds are well-supported by the tightly-knit but sometimes fractious Pontiac aftermarket community, and include
Nitemare Performance,
Tin Indian Performance,
SD Performance, and
Butler Performance. So who wins the big-block Pontiac vs. small-block Pontiac battle? It's the mack-daddy 455ci big-block, but you can always call it a stroked and poked 326 small-block if you like!
