Nov. - Dec. 2002 Motor State Performance Report Article By Jim Kaekel, Jr.
The subject of camshaft degreeing came up during a bench race session a while back, and the upshot was, with five racers taking part, there were three different philosophies concerning this vital process. Among this motley group, two racers saw little or no need for cam degreeing, one "sat on the fence" where degreeing was concerned, and the remaining two religiously degreed every cam they'd ever installed. To each his own, but we might add that of the five gathered here, only two ever managed to keep their engines together, week after week, and win with any consistency. That's right, it's the same two guys who degree their cams. The other three have lucked out occasionally and come close to winning, but their chief clams to fame involve the horrendous piles of trashed engine parts they've left behind at just about every track on which they've ever raced. Enough said. Degreeing the camshaft, while not the only key to winning a race, is certainly one of the surest ways of keeping everything working in "sync" so the car will at least still be around at the end of the race. Remember, inside every conventional race engine there are different tolerances for matching of cranks, cams, blocks, etc. Couple this with the phenomenon of reciprocating masses (pistons and rods) and, unless everything is working in perfect unison, the potential for real disaster exists.
Crane Cams offers the simplest definition of cam degreeing in their latest catalog. According to them, degreeing can be thought of as using a dial indicator and degree wheel as tools to map out one complete revolution around the cam lobe. Starting on the base circle of the lobe, where there is no lift, you will proceed up the opening side, go over the top of the lobe, and then move down the closing side, finishing back on the base circle. During this single revolution, the dial indicator will move from zero to the maximum lobe lift, and then back to zero once again. Watching the indicator, you will stop at two key points to take readings. Both points will be when the dial indicator shows exactly .050" of lifter rise. This reading will occur on the opening side and again to the closing side of the lobe. These readings will then be compared to the specification card packed with the cam to see how closely the two match. If necessary, corrections can be made to put the cam in the exact position.
Let's consider a word or two about corrective measures if things are not what they're supposed to be. Most performance timing chain sets have three or more keyways machined in the crank (lower) sprocket so the cam can be advanced or retarded. There are also offset keys available to further modify the advance or retard functions. Another method involves the use of offset eccentric timing bushings which can be installed in the cam (upper) sprocket to change the cam's position relative to the sprocket on those cams that use a dowel pin for indexing. After employing either method, degree the cam once again to be sure it is correct.
Here are some guidelines to keep in mind when degreeing a cam, courtesy of Crane Cams:
Keep in Mind that degreeing is vital to building durable, long-lasting race engines. It is a darn good idea for high performance street engines, too. The time spent will be well worth it if the engine lives for a long time...and wins a bunch of races to boot!