Whether you're an experienced engine builder or a weekend cruiser, you've probably heard the term "camshaft degreeing." To most, it brings visions of expensive precision equipment, complicated mathematical formulas, and lots of time. Contrary to popular belief, however, an advanced degree is not required when it comes to the timing of your camshaft. When broken down into simple steps, camshaft degreeing is as easy as setting valve lash, and takes about as much time. The tools you will use are probably in your box already, and if not, they are easily attainable and not very expensive. This article will detail the reason for camshaft degreeing, as well as take you through the steps to properly degree your camshaft.
The one and only reason to degree a camshaft is to ensure that it is properly phased (timed) with the crankshaft. It is really that simple. Keep in mind, that by degreeing the camshaft we are not changing the camshaft centerlines or timing, we are simply making sure that when installed, the cam's relationship with the crank is as the manufacturer intended. We have all heard that by advancing or retarding the cam timing, an engine will make more power or torque at a certain rpm. We have seen this method used with varying degrees of success, and in our opinion, if it is necessary to change your cam timing to achieve your goal, your application probably needs a different camshaft (the exception being certain stock racing classes). Companies such as Comp Cams have hundreds of camshafts to meet virtually every application and will custom grind a cam to meet your needs, changing the specs and centerlines if necessary. Our purpose is to give details on degreeing the cam, only changing the cam timing to the extent necessary to correct improper phasing.
In a perfect world we would not have to check camshaft-to-crankshaft phasing because all of our components would be manufactured accurately. This, however, is not a perfect world, and many factors can cause improper camshaft phasing. Improper cam or crankshaft machining, misindexed keyways or dowel pins, improper timing gear markings, or an accumulation of machining tolerances are the leading causes of improper camshaft phasing. It is usually not the camshaft itself, but the way the other engine components are manufactured or machined that necessitates degreeing the cam.
The following instructions will allow you not only to check your camshaft timing, but also to correct it if it is not right. Of the several accepted methods to properly degree a camshaft, we will outline the intake centerline method, as it is the easiest to understand. While this procedure can be accomplished with the engine in the car, the best time to degree the cam is during engine assembly. For our example, we will be installing a Comp Cams (PN 21-231-4) solid flat-tappet camshaft, lifter, and spring kit into a '68 440 HP, which is destined for our '68 GTX clone. The procedure is the same, whether you are working on small-blocks or Hemi engines.
Aside from basic hand tools, you'll need a few specialty items. Most of these are common if you assemble your own engines, and will complement your toolbox if you don't. First, you'll need a degree wheel and a pointer (the pointer can be made with coat hanger wire or the end of a scribe, as we used). The degree wheel is basically a round piece of sheetmetal with the 360 degrees of a circle printed on it. This, along with a pointer, tells us where the crankshaft is during its rotation. Next is a dial indicator with a magnetic or mechanical base to keep it stationary (be sure your dial indicator has sufficient travel to accommodate your cam's lift). A top-dead-center piston stop needs to be used if the heads are already installed. If not, you can use the dial indicator on the piston to determine top-dead-center before installing the head. If your combination utilizes hydraulic lifters (ours doesn't), you'll need a solid lifter that fits your engine. Also, an adjustable pushrod length checker (we made ours from an old pushrod) is used in engines that don't have adjustable rocker arms (ours are adjustable). Comp Cams has a degreeing kit available, which includes all of the necessary tools with the exception of the solid lifter and the pushrod length checker.