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Turbo Engine: Turbo Small Block Build

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What fails in the crankshaft, besides lack of oil and spun bearings from assembly errors, is a failure in the area of the fillet in the main bearing journal. The K1 crankshaft has a full-radius fillet on the main and rod bearing journals that relieves the stress in this critical area. The crank is also a 4340 forging, with a tensile strength approximately three times as that of a cast crank. Basic metallurgy indicates the higher hardness, the higher the tensile strength, and the greater the resistance to fatigue.

The H-beam rods are also made from 4340 steel. As we mentioned previously, it's not horsepower loads that breaks a rod. If it were, you'd see more rods crushed from the cylinder pressure. Most rods are pulled apart by the forces generated by the crankshaft. The design of the H-beam in addition to the hardness of the steel resists this type of failure.

When you combine the materials in the forging, the design of the H-beam rod, and the stress-relieved crank, you get a rotator that will take more cycles under more load over a longer period of time than any cast assembly. This kind of insurance will allow us to focus on testing parts and making power without worrying about failures on dyno day.

The Block
We all know Dart Machinery makes blocks, but what to choose? The SHP block is a stout piece at $1,500, but to use Dart's Jack McInnis' words, "The Little M is more suited to lots of power and lots of abuse." That sounds like us. We chose the Sportsman version because it is $400 cheaper than the Little M. It lacks four-bolt main caps on each end and it's made from ductile iron instead of billet steel, but it's stout enough for the kind of street/strip beating we will deliver.

Typical first-generation iron small-blocks are weak where the main caps meet the web in the block. If there is enough cylinder pressure and rpm, the webbing will crack and the crank bearings will turn to paste. Similarly, the main webbing can also separate from the crank, driving the entire rotator through the pan. To avoid these annoyances, the Little M Sportsman has more meat in the main webbing, more nickel alloy mixed in the casting of the block, and four-bolt splayed caps that don't squirm when you are at full throttle.

Another advantage to an aftermarket block is bore size. With a standard small-block, you get 4.030 or maybe 4.060 bore at best. Sure, you can go more with a 400 block, but at 1,000 hp, look for cracks that go from the steam holes to the head boltholes. The Little M can go all the way to 4.185 and still have 0.200 inch left in the cylinder wall.

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