How To Degree A Camshaft

With our big-block Chevy at 0.050 inch on the opening side of the lobe from max lift we recorded 62 degrees after top dead center (ATDC) and then 151 degrees ATDC at 0.050 inch from max lift on the closing side. Adding these two numbers together and dividing by two will give you the intake centerline. In our case: 62 + 151 = 213 / 2 = 106.5 degrees ATDC. The Comp Cams timing card supplied with our cam calls for an intake centerline of 106 ATDC, so we're within 11/42 degree of dead on. This told us that despite the numbers being off slightly at 0.015, the cam is installed correctly.

You back the engine up to 0.100 inch on the dial indicator before taking the reading at 0.050 on the opening side of the lobe because traveling past the data point and then turning the engine clockwise to approach the 0.050-inch data point removes any slack that may be present in the timing chain that resulted from turning the engine backward. This is why you don't turn the engine counterclockwise to 0.050, but rather go past it and then turn clockwise up to the first checking point. It's a small point, but accuracy is our goal.

This is the Comp Cams timing card that comes with every camshaft. Note that Comp only gives valve opening and closing numbers at a 0.015-inch checking height rather than at 0.050.