427/434
Once you step up to an aftermarket block, new opportunities abound. The 4.000-inch crank that's such a bear to fit into a production block drops inside an aftermarket unit easily, thanks to spread-out oil pan rails, a raised cam location, and in some instances pre-clearanced cylinders. Likewise, thick cylinder walls can be bored to 4.125 or 4.155 inches with room to spare, netting a total of 427 and 434 ci, respectively. Taking a page from the infamous Rocket block's playbook, aftermarket castings from Dart, World Products, and Brodix can be had as tall as 9.300 of deck height inches. That extra space allows the use of longer connecting rods, which means that the pistons aren't pulled as far down the bore, further reducing clearancing requirements. Thanks to the flexibility afforded by commodious aftermarket blocks, there are very few drawbacks to these two big-bore combinations.

454/468
The mystique alone may be enough to convince many enthusiasts to build a 454 ci small-block. Like its legendary big-block brother, that displacement total can be achieved with bore and stroke dimensions of 4.250 and 4.000 inches, respectively. While most aftermarket block manufacturers advertise a maximum recommended bore of 4.185 inches, World Products sells complete crate motors based on its Motown blocks that are bored to-you guessed it-4.250 inches. Obviously, with the small-block Chevy's 4.400-inch bore spacing, that doesn't leave much meat between the cylinders, even with Siamesed bores. However, cutting-edge innovations in gasket technology make a tight cylinder seal possible. "I wouldn't hit it with a power-adder, but with a multilayer steel gasket you shouldn't have any problems running a 4.250-inch bore in a small-block Chevy," Judson states.

For those who aren't entirely comfortable with paper-thin cylinder walls, stepping up to a 9.300-inch deck height block affords the same 454ci total by combining a 4.185-inch bore with a 4.125-inch stroke. Both Dart and Brodix offer blocks that have plenty of clearance for the massive stroke this combination requires. Match that lengthy stroke up with a 4.250-inch bore, and the displacement hits an astonishing 468 ci. Both 454's and the 468's have the obvious appeal of mega inches, and companies such as Eagle, Callies, and Ohio Crankshaft actually stock 4.125- and 4.250-inch cranks on the shelf. However, cranks with such long strokes sometimes become difficult to balance, as their shortened counterweight heights-necessary in order to clear the piston skirts-often require adding lots of mallory. Furthermore, 4.185- and 4.250-inch bore pistons will most likely be custom items.

496
Much like the 383 small-block, the 496 is downright puny by today's big-block standards. On the other hand, it is stupid-easy to put together and can be built from an abundant supply of cheap factory blocks piled up at junkyards. The formula is simple: Clean up a 454 block 0.060 over to 4.310 inches, and drop in a 4.250-inch stroker crank. Whether paired with 6.135- or 6.385-inch connecting rods, the 496 leaves plenty of piston material above the wristpins at the big-block's standard 9.800-inch deck height, which is a nice insurance policy if big power-adders are in the cards. And due to its sheer popularity, there are dozens of shelf pistons in varying compression heights to choose from. "At most, you might have to touch up the bottom of the cylinders slightly to fit a 4.250-inch stroke into a 454 block," Judson explains. "It's an old-school combination, but it still works very well."