How do I degree a cam?

Question:

I bought a hotter street cam from Pro Cams to install in my 1968 Camaro with a small-block and was told by a friend that I would need to degree the cam in. Is this true? If so, how do I do that? I will be using hydraulic lifters and the original rocker arms.

Answer:

It is not absolutely necessary to degree in your new cam, but it is a good idea if you want maximum performance. To do it you will need a degree wheel available from sources such as Summit Racing, and you may need offset bushings to correct any discrepancies, or possibly an offset crankshaft drive gear. Your cam was precisely machined for its application, but as you assemble your engine and install the various components you may have to deal with what is called “tolerance stacking,” in which tiny discrepancies in the machining of various components cause the cam to be out of adjustment by a few degrees.

Once the cam is inserted into the engine, its gears attached and the timing chain installed, attach the degree wheel to the crankshaft timing gear.

You can use a machinist’s magnetic stand and a dial indicator if you have them, but a simple and sure way to determine top dead center is to install a piston stop. You can make one of these out of 1 ⁄4”-thick steel strap by drilling a couple of holes in it to coincide with head bolt holes, then drilling and tapping a hole in the center and installing a fine-threaded bolt. The strap attaches to the deck of the block over a piston. The bolt is installed so the piston will not bump against it before it reaches top dead center. Then you turn the crankshaft until the piston just bumps the bolt on the positive stop and note down the reading on the degree wheel.

Next turn the crankshaft back the other way until the piston just bumps the stop, and note down your reading. Add these numbers and divide by two. This will give you exact top dead center for the piston. From there you can accurately measure the lobe centers on your cam. If your cam is within specs plus or minus a degree, leave it alone because cams are ground a little out to account for wear in the timing chain, but if your cam is two to five degrees out, you should correct it.

You can degree it in precisely if it is out beyond allowable tolerances by using a crankshaft gear that is offset, or you can drill out the holes in the cam timing gear to 11⁄32” and install eccentric bushings to nudge the gear two or three degrees in the right direction. Install the bushing with a little Loctite, and swage it in so it won’t fall out. Moving the cam in the direction of engine rotation retards the cam, and moving the cam counter to the direction the engine runs advances the cam.

If you are degreeing in a cam for the first time, double-check your work and your figures, and get an experienced friend to help, if possible. It all sounds more complicated than it is though. Gather the tools, follow the instructions step-by-step and you’ll soon figure it out. And when you do you will ensure that your engine will perform to its maximum.