Since we worked on the head and valvetrain in our budget B-series build this month, we figured now would be a logical time to cover a camshaft basic. One of the keys to making power is to properly set camshaft timing; in other words, when valves open and close in relationship to the position of the piston and crankshaft is critical to the performance of the engine.
The process of properly setting the camshaft position is referred to as "degreeing the cam." Many beginner tuners mistakenly believe that to degree cams means setting the cam gears at a certain position such as "+1 intake and -2 exhaust." Though this information may be useful at times, these settings may not be accurate on all motors.
For example, when the deck of a head or block is machined, it will retard the cam timing. So the cam gear setting method may only apply to engines using the same type of cam gears with exact same head and block heights. This also assumes that the given cam gear settings are the correct location for the cams.
The most accurate way to set camshaft position is to properly degree the cams. This way you can be sure the cams are in the right position regardless of engine variations, deck heights, and cam gear marks. The method we are proposing is a simple way for setting cam positions using peak lift measurements. Cam degreeing can also be used to check valve opening and closing positions, durations at various lifts, and peak lift measurements.
Helpful Tip 1 When degreeing a camshaft, make sure that you rotate the crankshaft in the
Step 1: Install a degree wheel onto the end of the crankshaft, and bolt a pointer onto the block. The pointer can be a sharpened piece of welding rod or coat hanger that can be bent to change the position of the pointer. Rotate the crankshaft to top dead center, or TDC, for piston no. 1. You can use a dial indicator inserted down the spark plug hole or the piston stop method; the piston stop method is more accurate. When the crankshaft is at TDC, move the pointer so it points to TDC/0 degree on the degree wheel.
Step 2: Set up the dial indicator with the tip on the retainer, NOT the rocker arm. To get an accurate reading, it is important to make sure that the axis of the indicator is parallel with the axis of the valve. Make sure the rocker is on the base circle of the camshaft; in other words, make sure the valve is completely closed, and zero out the dial indicator. We recommend that you degree the cam with the lash set at 0.000-inch.
Helpful Tip 2 If you are having a hard time finding the centerline because the cam dwells
Step 3: Rotate the crankshaft. When the cam starts to open the valve, the dial indicator will show the amount of valve lift. Rotate the crankshaft and stop when the pointer is pointing at the specified peak lift/center line position. Loosen the cam gear bolts and rotate the camshaft until the indicator is showing that the cam is at peak lift. Tighten the cam gear bolts. Rotate the engine two more rotations, stopping when the dial indicator reaches peak lift, look down at the degree wheel to make sure the position of the crankshaft is in the correct location. If not, repeat step 3.
Step 4: Move the dial indicator to the other side of the head, and repeat steps 2 and 3. When peak lift positions of both the intake and exhaust cams are set in the proper locations, the cams are considered to be degreed in.