Although it was never plopped into a production car, the hot rodding community went berserk when GM introduced the 4.468-inch Siamese-bored 502 big-block. Engine builders promptly punched the block out to 4.500 inches, threw in a 4.250-inch crank, and scored an easy 540 ci. Since they are basically 496s with a larger bore, 540s are just as easy to build. They require minimal clearancing and have tons of shelf pistons available in varying compression heights. Better yet, the 502's greatest asset is its rugged construction. Revisions GM implemented into the 454 block to create the 502 include reinforced deck surfaces for improved head gasket sealing, and four-bolt main caps. Racers have been known to push the 502 block well beyond 1,000 hp with surprisingly reliable results. Even if you can't find a good deal on a used 502 block (PN 10237292), they're available from Summit brand new for under $1,800. More often than not, it won't cost any more to build a 540 than a 496. It's no wonder why the 540 has become one of the most common big-block combinations built today.
And it gets even better. GM advises against boring a 502 block beyond 4.500 inches, but it's typical for racers to punch them out to 4.560 inches without any hiccups, netting a total of 555 ci. Boring the Rat out any more requires an aftermarket block, but a 4.600-inch bore in conjunction with a 4.250-inch stroke equates to 565 ci. Again, off-the-shelf pistons are plentiful for 4.500-, 4.560-, and 4.600-inch bores, and these seriously large holes can assist in cylinder-head breathing tremendously.
If hood clearance is an issue, or you seek to build something ultra-stealth, the 582 is the hot ticket. A 4.375-inch stroke is about as large as a standard 9.800-inch-deck-height block will accommodate, but standard-deck aftermarket blocks swallow them up without a fuss. Combined with a massive 4.600-inch bore, the result is 582 ci. Compared to a 540, the downside is that it requires an aftermarket block, so plan on coughing up a few extra bucks to play in this arena. However, the extra dough buys an extremely stout bottom end begging for a power-adder. This is yet another combination that can be built entirely from shelf parts, and there's just something sinister about packing close to 600 ci in a package that looks externally identical to a miniscule 396.
With the max bore pegged at 4.600 inches, increasing the deck height to 10.200 inches is the only way to gain additional displacement after the 582 mark. If you have the space underhood, this opens up several options. A 4.500-inch crank nets 598 ci, while a 4.750-inch unit tallies up 632 cubes. Furthermore, ponying up for a 10.700-inch-deck block allows running a 5.000-inch stroke, bringing the displacement grand total to 665 ci. The number of parts suppliers at this level shrinks a bit, but there are still plenty of shelf components to make it all happen. Both Dart and Brodix have 10.200- and 10.700-inch-deck blocks with raised cam locations that will clear up to a 5.000-inch stroke, and Callies offers the necessary cranks. Shelf pistons are readily available for the 598 and 632, while the 665 will most likely require customs. To keep the rod/stroke ratio reasonable, rod lengths from 6.700 to 7.100 inches are highly recommended. The only real hitch here is cost, spending the necessary funds to bolt on a set of cylinder heads that can keep up with the voracious appetite of this many inches.