These days it's unbelievable how easy it is to make obscene levels of horsepower. But whether an engine is blown, turbocharged, nitrous'd, or even naturally aspirated, it's also easy to quickly surpass a stock engine block's ability to handle the gobs of power that can be made with readily available heads, intakes, and valvetrain parts.
Over the years, a few relatively scarce factory race blocks have been produced, such as Ford's famous 427 side oilers, and the Mopar Max Wedge and Hemi blocks. It used to be that the strongest factory production blocks came with main caps that utilized four fasteners to hold the crankshaft in place. Also known as "four-bolt mains," these blocks were generally thicker and provided superior clamping forces over the conventional two-bolt-main units by preventing the crankshaft from moving or wandering around at high rpm, which can be detrimental to the life span of any rotating assembly. Most engine builders prefer to base their performance engines on good blocks used in conjunction with forged internals consisting of the crankshaft, rods, and pistons to greatly reduce the chances of a catastrophic failure. Unfortunately, these heavy-duty blocks are getting harder to find at the average yards, which ultimately gives sellers an excuse to charge a remarkably high premium, and even the beefier factory blocks can leave a lot to be desired when building a race engine.
But the rarity, age, and price of these old castings hardly makes them viable for the legions of racers and serious street machiners with a need for speed far in excess of a junkyard block's capacity. Fortunately, there are now a plethora of options for aftermarket blocks for just about every major brand. These blocks are far superior to the factory production units and offer much more efficient water and oil passages, greater displacement capacity, and the ability to withstand just about any power level you can throw at them. Of course we're not saying everyone needs a race block to build a 400hp street engine, but if you're looking to eclipse the envelope of a stock block, it's only a matter of time before even the stoutest will give up the ghost. Believe us, waiting to pitch a crank out of the bottom of your engine is a terrible game of Russian roulette to play after you've invested all that time and money in a killer power combo. So if you're serious about making big power, read on to see what's currently available to help guide you to consistent and reliable performance.
ZL1 AluminumFirst introduced in the '69 big-block Corvette and Camaro, the aluminum ZL1 is one of the rarest production engines ever built. While the newer version is based on the original tooling, the improved casting is constructed of 356-T6M aluminum alloy and can handle up to a 4.300-inch bore with maximum 4.375-inch stroke (that's 508 ci). The bottom end features four-bolt, splayed, steel main caps, and includes screw-in freeze plugs with O-ring seals and a two-piece rear-main oil seal. It's also compatible with just about any cylinder heads listed in the GM Performance Parts lineup. We especially like the fact that the ZL1 weighs a mere 110 pounds. It might be a little spendy, but if you can afford it, you'll have the coolest engine bay in town.
PN: 12370850Block material: AluminumDeck height: 9.800 inchesBearing-cap type: 8620 steel four-boltMain-journal diameter: 2.75 inchesOil system: Wet or dryCylinder-bore range: 4.118 to 4.300 inchesMaximum stroke: 4.375 inchesMaximum displacement: 508 ciWeight: 110 poundsPrice: $5,115.45