You just opened the box containing that new monster cam you bought for your hot rod and you can hardly wait to simply slide that baby in place. Piece of cake, you reason. It's going to make your car rump and shake like a Pro Stocker, and it's certain to produce more power than any other machine on your block. But is installing it really a no-brainer? Not exactly. If you install the cam correctly the first time, you will reap all of its rewards. If you don't, you'll be driving a heap. How do you know if it's installed correctly, you ask? Well, you can either rely on your keen ability to "see" within your engine and "read" the cam's figures as they actually occur. Or you can degree it.
Degreeing a cam is a simple and effective way to ensure you've got the cam you were looking for and you've installed it correctly. Even with today's cam companies using some of the best computer-controlled cam grinding equipment available, there's still the chance for operator error. The cam grinder could have machined the wrong lobes, or the packaging department could have put the wrong label on the box. Either way, you'd never know unless you degree the cam.
In addition to a degree wheel...
In addition to a degree wheel and dial indicator, you'll need a positive piston stop to find true TDC. Pictured is a deck strap-style stop from Powerhouse that bolts onto the block when the heads are removed and a screw-in brass stop from Crane that's center-drilled to let air escape when it's screwed into the No. 1 spark plug hole.
There's often confusion about what degreeing a cam really means. In its simplest definition, degreeing the cam is a means of verifying the installed position of the cam relative to the crankshaft; i.e. "advanced, retarded, or straight-up," and it's also a way to confirm that the cam was ground correctly. Degreeing a cam is not the same as advancing or retarding it as some people mistakenly believe. Degreeing the cam involves bolting a precisely-marked wheel onto the crank or damper, which will indicate crankshaft position, and then checking the cam lobes at a specified lift. Most degree wheels are numbered in 180-degree increments moving away from both sides of Top Dead Center (TDC). Although there are other ways to mark the degree wheel, such as 360 degrees from TDC and also in 90-degree increments, wheels marked 180 degrees on either side of TDC are generally the easiest to use.
Finding True TDC
This is the most important part of correctly degreeing your camshaft and if it's not done properly, your results will be worthless. Fortunately, it's also the simplest part of the process. Start with the No. 1 piston approximately at TDC. This can be done by placing your finger over the No. 1 spark plug hole and turning the crank clockwise until air pushes out. Watch the damper for the TDC or 0-degree mark to come up and stop rotating the engine when TDC is indicated on the damper. Install the degree wheel and align a fixed pointer (coat hangar wire works well) with the TDC mark on the degree wheel mounted on the crank snout or damper. Don't worry about getting it exact yet, that step is next.
You'll need a 1-inch dial...
You'll need a 1-inch dial indicator mounted securely to the head or block and some type of extension to reach the No. 1 intake lifter. Always use a solid lifter only.
Now turn the crank counterclockwise until the wheel reads about 90 degrees and thread a positive piston stop into the No. 1 spark plug hole or strap a piston stop on the deck if the heads are off. Carefully turn the crank clockwise until you feel the piston touch the stop. It helps to have a hole drilled in your piston stop to bleed off cylinder pressure as the piston moves up the bore. With the piston touching the stop, mark the degree wheel or write down the number, i.e. 64 degrees. Next, reverse direction and rotate the crank counterclockwise until the piston touches the stop again and mark the wheel or write down that number, i.e. 70 degrees.
The difference between these two readings is 6 degrees. Move the wheel or wire half that distance (3 degrees) to indicate 67 degrees on the wheel. Switch direction again and rotate the crank clockwise, and if you did it right, the wheel should indicate the same number when it touches the piston stop in either direction, i.e. 67 degrees in this example. Once you've got it stopping on the same point in either direction, the wheel will correctly indicate TDC with the piston stop removed. Do not move the wire or wheel after this point.