Know-How Notes: How A Camshaft Is Made
An engine is a complex piece of machinery. There are hundreds of moving parts that all have to work together in a coordinated effort in order to function correctly. One of the key components to managing this effort is the camshaft. Sometime called a “bumpstick” or “cam”, this the component that tells the valves when to open and close, as well as drive the distributor (or tell the computer when to fire in EFI applications). For GDI (direct-injection) engines, the cam also runs the mechanical high-pressure fuel pump, so suffice it to say, the cam is critical to the engine’s operation.
Over time, the camshaft can wear down or become damaged, requiring replacement. For high-performance applications, a cam swap can take stock low-output engine and turn it into a fire-breathing monster. The process of creating this critical component is quite unique, so we visited Comp Cams’ facility in Memphis, TN to see exactly how a camshaft is made.
The design process is different for every application, but the basics are the same – create a profile for the intake and exhaust lobes for the type of engine the cam is for. There are several types of camshaft used in automotive applications: flat tappet, roller, and subsets of each for hydraulic or solid lifters. There are also two places where the cam can be located: inside the engine block or on the cylinder head (also known as an overhead cam). For this article we are going to talk about engines that have the cam within the engine block. Cam design is very complex, so we will be focusing this article on the actual construction of the camshaft. For that, you need to know the basic anatomy.
There are five basic segments of a camshaft: lifter lobes, bearing journals, gear mount, distributor gear or timing lug, and fuel pump lobe. Not all cams have all five, but they will all have the first three. The bearing journals are the surfaces that the cam rides on inside the engine block. The cam bearings are installed in the block journals, and feed oil to the cam, keeping it lubed and spinning. The cam gear mount is where the timing gear bolts to the camshaft. This is how the cam is driven inside the engine. This is usually part of how the cam is secured in the block as well. The lifter lobes are where the magic happens. This is what drives the lifters, which operate the valves to allow the air/fuel mix in and the combustion gases out in the right sequence. The other segments are there for a mechanical fuel pump and distributor or cam sensor.
If you talk to any hot rodder about cams, they will often call the profile a “grind”. This is because that is how the cam gets its profile; it is ground into the metal. There are two main types of camshaft starting forms: cast and billet steel. A cast cam is the most affordable. These are cast forms that are created with a general lobe design already formed into the part. These generic lobes are then ground with the corresponding profile by the machinist. Small changes can be made with these designs, so these are reserved for high-production profiles.
For custom grinds, a billet steel slug is used. There cams cost more because there is a lot more work involved, yet Comp Cams can produce custom grinds in just a few days. With a billet cam, every aspect of the cam has to be machined; there are no separations for the lobes, distributor drive, or journals. These segments are cut individually before the profile is ground.
To do this, there are two machines used: a traditional grinding lathe, and a CNC machining center. The CNC version can do all of the processes, and it used for most billet grinds. The grinding lathe is operated by hand, and it is very cool to watch. There are two stages: rough grind, and finish grind. For cast cams, this process is very quick.
The lathe uses a follower cam, much like the camshaft in your car, except that on the machine, the cam lobe rotates against a solid lug. The cam lobe moves the spinning camshaft, changing its position against the spinning grinding wheel. The operator switches between the intake and exhaust lobes, the entire process takes just a few minutes. Once the rough grind is done, the cam moves to the finishing machine where the most senior operators make the final passes with a very fine grinding stone on a same type of machine.
When complete, the cams go to the checking room. Here each cam is put through several tests to verify the grind profile and quality control. A large computer-operated testing device measures the cam with very tight tolerances, ensuring that every cam that goes out the door meets exacting specs.
High Tech Treatment
Some manufactures now offer high tech new coatings that can further protect a cam from wear. For example, COMP Cams®’ Pro Plasma™ Nitriding is a patented, 36-hour process that uses pulsed nitrogen plasma in a vacuum-controlled environment to embed chains of nitrogen ions into the camshaft surface approximately .008” to .010” deep. “Our extensive testing here at COMP Cams has confirmed a 100 percent increase in strength and lubricity of the camshaft’s lobe surface for improved durability” said Billy Goldbold, COMP Cams Valve Train Engineering Group Manager. “This fortified new outer layer is not a coating or polish. Rather, there is an actual change to the outer layer of the camshaft metal’s chemistry. The diffused nitrogen is forced into the iron lattice structure, increasing hardness and strength, while greatly reducing sliding friction,” he went on to say. Because the surface where the lifter rides on the lobe is subjected to such severe pressures, nitriding makes a big difference in extending the life of the cam. Coatings like this are becoming more commonplace as modern engines can deliver higher performance than ever before.
From start to finish, that is how a camshaft is created. Next time you need to swap cams, you will know exactly what goes into the creating that voodoo magic that controls how your engine functions.
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