Hard-core Parts
Any engine--crate or otherwise--begins with the block. The block is the foundation because it houses the rotating assembly (consisting of the crankshaft, connecting rods, and pistons), the cylinders, and passages for coolant and pressurized oil. Many blocks have provisions for installing a camshaft. But the block's job doesn't end there. Cylinder heads are bolted tightly to the block, and their retaining hardware must keep the heads sealed, even under the extreme pressures of combustion. There's also a variety of front engine access-ories mounted to the block, all of which vibrate, twist, and/or turn. And let's not forget the transmission and the engine mounts that hold it all in place. Whew! As you can see, the block serves many duties, but its biggest jobs are to contain the rotating assembly and to deal with the immense forces, vibration, and friction.
When it comes to stock, late-model, 5-liter blocks, there most certainly is a limit. When you double or triple the level of power, cracks can develop and failure occurs. As horsepower or rpm is increased, so are the forces on the block, which is why it's necessary to upgrade the engine block when you get to a certain horsepower level.
But what is that level? Unfortunately, there really is no accurate answer. It all comes down to the preparation and the usage. Some stock blocks have lived well past 600 hp, others crack while making 350. The fact is, the stock 5.0 blocks are of the thin-wall cast type and are susceptible to cracking in the main web area. It is this author's belief that excess vibration and detonation will kill a block quicker than excess horsepower will.
Like the block, the crankshaft is also subject to some unbelievable forces. The crank has the dubious job of converting the up and down motion of the pistons into rotational force at the flywheel. There are a few different materials used to manufacture cranks. The most common is nodular cast iron, which is mostly used in stock engines. When prepared properly, a stock crank can handle 400-500 hp, assuming the engine is not revved regularly past 7,000 rpm. Of course, a quality balance job and lightened rotating assembly goes a long way to keeping a crank alive. Also, deburring the casting will reduce the chance of a crack starting, and chamfering the oil holes also helps.
Forged steel cranks are certainly stronger than nodular cast iron and should be used if you can afford one, or if you plan to buzz the engine past 7,000 rpm. In either case, you should spend the money to have a used crank Magnafluxed to ensure there are no cracks. Last on the crank-shaft list is the billet steel crank. These are cut from a steel billet and are the strongest of the crankshaft lot.
Along with a good crank, you'll want to purchase quality connecting rods, wristpins, and forged pistons for any performance appli-cation. We always suggest buying the best parts you can afford, and strongly advise not buying inferior parts or used parts unless you know their exact history. You will only wreck them and have to spend more cash on the right parts down the line.
While the bottom-end of the engine provides the strength, the top-end provides the power. Airflow into the cylinders (combined with a proper fuel mixture) is where the power comes from, so you'll need a combination of cam, heads, and intake (and power adder, if applicable) that works in unison. It's downright impossible for us to offer up any single combo that will work for each and every person who reads this article, so you'll be left on your own to research and pick those parts. But do understand that you probably don't need as much cylinder-head flow or camshaft lift as you think. By keeping on the small side, the airflow will maintain port velocity, and that equals volumetric efficiency (VE). And good VE equals torque, which we all know is the key to having a strong street engine. This is yet another reason to deal with a Ford-specific engine shop.
"Fords are our mainstay, so we're well versed, and we'll be able to help you select the best cam or heads for your combination," says Huff of CHP. "A typical rebuilder might not know which manifold is best, or he may not have tried a variety of aluminum heads on different engines. Or, he may have to order parts including all the little stuff, where we have it all in stock. In addition, our sales staff is made up of Ford racers who know what you're trying to achieve.
"Generally, it takes a week or two to get an engine. We stock short-blocks and then dress them as needed for each customer. That way, we can get a fix on the combination."