“I’ll have a BTR Stage 7 Super Nitrous Turbo Thumper 3/4-Grandaddy camshaft for my 5.3 LS, Mr. Sir, please and thank you,” says the guy ordering way too much cam for an otherwise stock LS engine. Even though this opening line was full of bologna, it got the door open to talk about camshafts. We are not talking about the design of the profile; this story isn’t called “how does a cam work,” it is “How a Camshaft Is Made.” No, there are no little camshaft gremlins from the nearby ethereal realm Valvetrania; it’s really just a bunch of machinery.

A blank cast cam looks like this; the profile is rough cast as it came out of the sand mold. The bearing profiles are typically machined in batches, as they are all the same per engine.

Anatomy of a Camshaft

A camshaft is comprised of five segments: lifter lobes, bearing journals, timing gear mount, distributor gear, and the fuel pump lobe. All cams have lifter lobes, bearing journals, and timing gear mounts; the other two vary by engine design.

Lifter Lobes

When you think of a cam, this is what you see: the egg-shaped lifter lobes that move the lifters in a cam-in-block engine up and down. In an overhead cam engine, the lobes either act on buckets sitting on top of the valve or a rocker arm.

Bearing Journals

Most cams have 4 to 5 bearing journals on the camshaft; these are the maximum diameter of the cam, and they ride inside the cam bearings.

Timing Gear Mount

You have to drive the cam somehow; the cam gear typically mounts to the front of the camshaft. This can be a bolt-on or a keyed gear.

Distributor Gear

If the engine uses a distributor, then the camshaft will likely have a drive gear. The drive gear meshes with the distributor and spins the rotor at the same speed as the camshaft.

Fuel Pump Lobe

Most engines built prior to EFI, as well as all direct-injected engines, use a fuel pump lobe on the cam to operate the mechanical fuel pump. For older engines, this is usually an offset circle, operating the pump once per rotation. DI engines use 3- to 6-sided fuel pump lobes, which operate the high-pressure fuel pump.

Billet steel cams are, as the name suggests, made from solid billet steel. This is a sample of a billet cam halfway through the machining process.

What Are Camshafts Made Of?

Specific camshaft profiles are also referred to as “grinds”, which lends a helpful hint as to exactly how a cam is made — they are ground. Pretty much all stock and most aftermarket cams are made from blanks cast from various grades of iron or steel, while specialty cams are made from billet steel. We went into more details on cam materials here.

Cast cams are typically made with chilled cast iron. The camshaft mold is made with a blank camshaft that has large, raw lifter lobes, allowing the blank to be used for most profiles. Each blank is made for a specific engine family, such as small-block Chevy, big-block Chevy, LS, small-block Ford, or Mopar big-block. Chilled cast iron is not a different material, but rather a process. Specific areas of the mold are rapidly cooled during the casting process. This yields a hardened, white outer layer called the “chill,” and a softer, forgiving inner core. The result is a harder outer layer for the lifter to slide over with less wear and a flexible inner core that absorbs shock and breakage.

A cam grinding lathe uses a follower guide (A) to trace the profile of the lobe master (B). There are two different lobes here, the operator moves the stack to position the correct lobe pattern against the follower.

Forged steel has been used for OEM and aftermarket cams throughout the years. GM stopped using forged steel cams in 1954 with the advent of the hydraulic lifter. Solid lifters induce more stress and shock on the cam than hydraulic lifters, making a forged cam a good choice. That said, most aftermarket cams are chilled castings. A bronze distributor gear is required when using a forged camshaft.

For high-end custom engines, billet steel or tool steel is used to form the camshaft. Billet steel blanks are raw steel billet “logs,” which have almost no features pre-built into the cam core. There are multiple reasons for needing a billet camshaft, including heavy spring rates, extreme lift, and high RPM. Every single parameter must be machined into a billet camshaft, from the bearing journals to the distributor gear, so these are more expensive and take longer to make. The benefit is that you control every aspect of the cam profile. Most billet cams are made from 5150 or 5160 steel.

A blank cam is mounted to the machine as the grinding wheel lubricant washes over it. You would never grind a cam dry. The operator moves the cam lathe into position against the wheel and the lobe begins to take shape.

How Is A Cast Camshaft Made?

There are two machines used to cut a cam profile: a grinding lathe and a CNC machine. For cast cams, the lathe is used the most. A cam grinder is a very large piece of equipment, about ten feet long by five feet wide. These are “follower” lathes, meaning they follow a simple pattern to reproduce the intended lobe profile. A V8 cam has 16 lobes, 8 intake and 8 exhaust. The operator loads the specific lobe guides onto the lathe, locks in the blank, and the machine grinds the blank into the matching profile.

The cam blank and the grinding wheel must remain in contact throughout the entire process, and the wheel must be perfectly flat. The lathe bed (where the cam is mounted) is spring-loaded on a pivot bar. The lobe pattern spins with the camshaft blank, ensuring that each lobe is clocked correctly. As the camshaft spins in the lathe, a follower guide rolls along the pattern, moving the blank back and forth against the grinding wheel, grinding the lobe profile into each lobe one at a time.

Once the rough grind is done, the cam moves to another machine with a higher-grit wheel to do the actual final shaping. Premium cam polishing goes up to 1,500 grit.

The operator runs the machine fast, then slows it down for a few rotations, and then disengages the machine, moves the follower guide to the other profile (exhaust), and cuts those lobes. The change in speed is due to the position of the stone on the lobe. Most cams are ground between 60 and 150 rpm; this is the rotation speed of the cam itself. The grinding wheel spins at 3,000 rpm. Each lobe profile is ground in several stages, with the rough grind being B126 (140-180 equivalent), B64 (230-270 grit) for the shaping grind, and finished with a B46 (400-500 grit) grinding stone. Custom cams are often polished with finishing tape. The machine does most of the work, but the operator controls the speed and timing, which can affect the final results.

Billet steel camshafts are usually machined before grinding to remove the bulk of the material. Usually, a billet camshaft is cut in a CNC machine, specifically a CNC lathe. This machine spins the cam blank while the cutter precisely removes material to create the cam’s features. There is usually much less operator input with the manufacturing of billet cams, so they have far more precise tolerances without much — if any — meaningful variance.

Fresh Bumpsticks, Hot Out The Oven!

Once machined, you could clean the cam up and slap it in the block, but that’s no fun (OK, it’s fun, but hear us out). There are a couple more steps needed to make a good cam great. First, you have to make sure the cam is the right profile. A digital measuring tool called a “flexible automated shaft gauge” (which are also known by the popular product or manufacture names such as “Cam Doctor” or “Adcole”) is used to measure the cam profile in all aspects including the bearing journals and lifter lobes to ensure that the surface is smooth, round, and has all the correct specs. The machine slowly spins the cam while the extremely precise follower rides along the surface. This helps camshaft manufacturers deliver pinpoint accuracy.

Finally, is the surface treatment. There are a number of options out there, but nitriding is one of our favorites for durability. COMP Cams uses an Eltropuls plasma nitriding machine to impart the nitrogen into the metal between .008 and .010 inch deep, which is about 10 human hairs. This is accomplished by pulling the chamber into a deep vacuum for 36 hours, while the metal is heated to around 1,000 degrees Fahrenheit. Once up to temperature, the chamber is filled with a nitrogen-rich gas, which hits the metal. The heat causes the nitrogen to separate from the gas, bonding to the metal. Plasma nitriding results in an incredible increase in surface hardness and lubricity, which means your new cam will last a lot longer than it would without nitriding.

After machining/grinding, the cams are checked for accuracy with a digital gauge that measures the cam and compares it to the master profile. If it is off even a little, to the scrap bin it goes.

What About Grinding Stock Cams?

Back in the day, before CNC machines took over the world of machinist manufacturing, the only way you could get a custom cam for some engines was to have the factory cam reground. This is done in a couple of ways. In the olden times, the base circle for each lobe (the wide part of the egg where the valvetrain is at zero lift) would be cut down in order to allow an increase in the lift and duration by regrinding the lobe. This can cause issues with getting the timing dialed in. You need an expert cam grinder for this type of modification.

Modern cam regrinds are performed by welding additional material to the ramp and nose of the lobe, typically Stellite, which is a family of cobalt-chromium alloys. Then the cam gets refinished using a grinding wheel lathe, just as a cast cam is ground.

Once the cam is ground, checked for quality, and nitrided, it is cleaned, coated with an anti-corrosion oil, and then bagged and boxed, ready to ship to your door. Cast cams can be ground in a matter of minutes, ready for installation, but billet cams can take up to a couple of days, which certainly affects the price. So next time you go looking for a camshaft, you can stay out of the cupboard in the closet; there is no need to visit Valvetrania, just the website of your preferred camshaft grinder.