Performance Camshaft Kit and Calibration - How To

When you buy a camshaft out of the box these days, you can be reasonably certain it will be close to where you need to be in terms of the grind. Much of that is because of advances in technology available to the cam manufacturers. However, as any good racer knows, you can never take anything as important as your camshaft at face value.

So, it's always a good idea to synchronize your camshaft to the crank before you count on it to deliver race-winning horsepower. There is no magic to degreeing your cam: simply bolt a degree wheel to your crankshaft and check it the way engine builders have done for many years. The purpose of degreeing a camshaft is to synchronize its rotating position with the crankshaft. This is the only way to know that the valves are opening and closing in accordance to the rise and fall of the pistons as intended for peak performance. To phase in the camshaft, the manufacturer's data (the cam card) has all the information you need on where that particular camshaft needs to be degreed.

To get a better step-by-step understanding of this process, Circle Track magazine went to Dave Pletcher of Pletcher Racing, Inc. to get useful cam degreeing info. Pletcher builds engines and drives his own Sprint car in the fast and furious world of the Tampa Bay Auto Racing Association.

The most common method of degreeing a camshaft is the centerline method, this will not work with most modern-day performance camshafts. While conventional lobes have the same shapes on both sides of the lobe, a modern-day camshaft's lobes are asymmetrical or not equal on both sides. Therefore, the industry-standard method to get an asymmetrical camshaft degreed correctly is to use the 0.050-inch of lobe lift method. This measures the camshaft at 0.050-inch of lift regardless of the shape of the lobes. "The 0.050-inch method is the only way a cam gets degreed in my shop," said Pletcher.

Finding True Top Dead Center (TDC) The first step in degreeing a camshaft is finding top dead center on the No. 1 cylinder. Once the crankshaft, cam, and pistons are assembled in the block, the timing gears are bolted on with their index dots/indents aligned. Now, rotate the engine so that the No. 1 piston is approximately at TDC. Next, the degree wheel is bolted to the crankshaft using a keyway for alignment. "Use the largest degree wheel you can find," Pletcher said. "The larger wheel has more room for the tic marks, making it more accurate, especially when it comes down to small differences."

A steel timing pointer (coat-hanger wire, for example) is mounted to the block and pointed at the degree wheel. Make sure the degree wheel's zero mark is aligned with the pointer. You may have to bend the pointer or rotate the wheel to achieve this indexing without turning the crank. With the degree wheel and pointer locked in position, you're ready to attach a piston stop to the block. "The most common problem I see is that people don't use a positive stop and only estimate top dead center (TDC)," Pletcher said. "Then the camshaft is off a long way. Finding the true TDC of the No. 1 cylinder is the most important step when degreeing a camshaft. The piston can dwell at TDC for 6 to 8 degrees of crankshaft rotation, making for a large margin for error."

Pletcher mounted a positive stop on the block over the No. 1 cylinder. There are a couple of ways to attach the positive stop. One type screws into the spark-plug hole and the other is strapped across the top of the cylinder (if the head has been removed). On the second type, which is the most accurate, a bolt extends from the stop into the cylinder bore. The bolt makes contact with the piston, stopping rotation. The bolt on the screw-in spark-plug hole stop sometimes cannot contact the piston in some of today's high-performance heads, particularly the aluminum heads, because of the spark-plug angles in such heads.