Camshaft 101 - Timing Tech

Checking and adjusting the camshaft timing can be a little bit intimidating to racers or first-time engine builders because it is a bit complex at first. But it is also vitally important because getting it wrong can cost you serious power. Plus, the ability to modify your cam timing can help tailor your engine's power curve to your needs.

Proof of this is the fact that students in the NASCAR Technical Institute's upper-level race engines class begin their course by spending an entire day or more discussing nothing but camshaft timing. Issues such as checking cam timing to make sure it matches up with your camshaft card, advancing or retarding the camshaft to influence power production, and even checking and understanding how such things as overlap, duration, and even total valve lift are taught as a foundation because it affects almost everything else.

We understand that long how-to articles about degreeing in a camshaft can make a reader's eyes glaze over, but when we heard instructor Craig Hibdon's methods for teaching camshaft timing and how well his students responded to it, we asked if we could base an article on his class. The NASCAR Tech Institute's method for degreeing a cam isn't unique; in fact, most engine builders follow some variation of this method. But the methods Hidbon uses to present these sometimes difficult concepts are about as simple and easy to understand as we've ever heard. So, turn to page one in your textbooks class, we're about to have some fun.

Finding piston TDCTiming your camshaft involves measuring total lobe lift, the lobe centerlines for both the intake and exhaust lobes, camshaft duration at 0.050-inch lift, and lobe separation. But before we can do any of that, we first have to find the crankshaft location when the piston in the number-one cylinder is at top dead center (TDC).

After you have installed your crankshaft and camshaft and connected the two with your timing set, take a moment to make sure you have your cam installed "straight up," which means the tick marks on the timing gears point toward each other. At this point, the camshaft should be installed as your cam manufacturer intended. But it should always be checked because any number of variables can throw off cam timing. These factors include, but are not limited to, an improperly marked timing chain, errors when machining the block, assembly errors, or even an improperly ground camshaft.

To find piston TDC, you will need a degree wheel attached to your crankshaft, a degree-wheel pointer, and a piston stop. Install the degree wheel on the nose of the crankshaft and position your pointer-often just a piece of wire-over the degree wheel, as close as possible without touching it. Your piston stop can thread into the spark plug holes or simply be a strap that pulls over the deck of the block. It doesn't matter as long as it keeps the piston from reaching TDC.

Slowly spin the crank clockwise until the top of the piston contacts the piston stop, and check the position of the pointer on the degree wheel. Count up from the zero mark on the wheel and make note of it. Now, slowly spin the crank counterclockwise until the piston makes contact with the piston stop again. And once again, make note of the degrees on the degree wheel in the direction closest from the zero mark. In other words, both of your readings should be less than 180 degrees. Now, find the average of those two numbers. For example, if your readings were 36.75 in the clockwise direction and 35.25 when turning the crankshaft counterclockwise, the average is 36 degrees.

Remove the piston stop and spin the crankshaft until the pointer is over the 36-degree mark, which is between your two readings. Your piston is now at TDC. Readjust your degree wheel-without allowing the crankshaft to move-so that the zero mark on the wheel is underneath the pointer. Now we are set to get to work.