You might think that the idea of balancing a camshaft is a solution in search of a problem. After all, unlike a crank, which is commonly balanced, a camshaft is very compact and any imbalance should have a limited effect on the engine, right? That may be true if you are running very conservative engine packages, but if you are trying to push your rpm limits, running an aggressive cam, or otherwise trying to push your engine to its performance limits, there might be something to be gained here.
Believe it or not, some race teams have been running balanced cams for decades now-just not in stock car racing. Mike Jones, owner of Jones Cam Designs, grinds custom cams for many different racing applications but got his start with Indy Cars. In the '80s, he says, teams began pushing the engine speed boundaries beyond 12,000 rpm. As they reached these incredible engine speeds, they began breaking camshafts. As a solution, some teams began experimenting with balancing the camshafts. This worked, but the method at the time was to actually create cams with small counterweights between the lobes. Other teams created small vibration dampers and attached them to the front of the cams. Jones says that the solutions not only helped solve the cam breakage problem, they also improved valve control. Unfortunately, both processes were very expensive, and the idea of balanced camshafts didn't catch on in sports outside the Indy Car realm where teams worked with nuclear-powered budgets.
In the past few seasons, however, Jones says that some Nextel Cup teams began experimenting with balanced camshafts as a way to increase valve control as they continued to push toward the 10,000-rpm barrier. Teams have seen positive results. Jones says that one team he has worked with has seen an improvement of 3 hp. It may not sound like much, but then again, how often do you come across a completely legal gain of 3 hp?
From his experience designing cams for all types of racing engines at all power levels, Jones believes there are benefits for using balanced camshafts in almost every application. If it was to be useful to the Saturday night racer, it also had to be affordable. To accomplish this, Jones designed a balancing system for his cams that is both simple and effective. Called the Cam-Wave Balancing system, Jones has found a way to balance camshafts using a balance plate bolted to the front of the cam and by performing a little machine work to the back.
"The cam is spun on a balance machine at 400 rpm," Jones explains. "Different cam designs for different engines vary, but our test cam was 4.8 ounce/inches out of balance. By adding the front plate, we were able to bring that down to within 1 ounce/inch. Then, by performing some machine work on the core of the cam, we can bring the imbalance down to 0.4 ounce/inch. That's less than 10 percent of the original imbalance."
To find out just how much a balanced camshaft affects valve control, we tested one of Jones' Cam-Wave units against another unbalanced camshaft with otherwise identical specs. For impartiality, the test was performed at an independent location, Roberts Racing Engines in Mooresville, North Carolina. For the test, we spun both camshafts on a Spintron machine set up with a Chevy block and SB2 heads. The test springs provided 175 pounds of pressure on the seat and 500 pounds over the nose. Cam specs for both cams were 0.424 inches of lift at the lobe and an identical 258 degrees of duration at 0.050 lift. Overall, it's a very common combination that should show us real-world scenarios.
As you might expect, the Spintron showed little difference between the two cams at lower rpm levels. As the rpm picked up, the differences became more obvious. As the setup with the unbalanced cam began showing signs of losing valve control, the Cam-Wave cam kept things in better control. At max lift, the valve didn't loft as much, and valve bounce was noticeably diminished. It's the valve bounce that was most important to us, since that can be responsible for valve and seat damage and also reduces cylinder pressure (which kills power).
As valve control increases-whether it's by using the Cam-Wave system or another method-it provides options. Depending on your needs, you can use the opportunity to increase the engine's maximum rpm level before the valves start going out of control again, you can go with a more aggressive cam lobe to increase power at the same rpm levels, or you can basically leave everything else the same and increase durability. Of course, many savvy engine builders will try to find the package that adds a little of all three.
Jones says one of his major goals when creating the Cam-Wave system is to make the price affordable to the racer who funds his program out of his own pocket. Fortunately, the simplicity of the system allows Jones to do that. He says that it should only cost approximately $100 more than a standard cam, but there is a catch if you want to add a timing chain set as well. Because the timing chain sprocket attached to the front of the camshaft is so large, it must be included in the equation when balancing the camshaft. For standard chain-driven timing sets, Jones chose to use SA Gear units with billet steel sprockets. This is because the billet pieces are much more consistent than cast pieces. Because of this and the fact that Jones grinds all of his own cores, the cams and sprockets are so consistent that every cam does not have to be physically balanced on a balancing machine. This plays a big role in keeping the costs down.
At the time of this writing, Jones also had developed a Cam-Wave system for use with a Jesel belt driving timing system for Chevy small-blocks. By the time you read this, he should also have completed designs for small-block Fords, big-block Chevy, and the small-block Chevy running the 4/7 cam swap.
Because there is virtually no one running balanced cams yet (except for a few NASCAR Nextel Cup teams that have so far been tight-lipped about results), it's still too early to tell just how helpful a balanced cam system will be in lower-level racing engines. Still, the Spintron at least hints that there is promise here. We're anxious to see how inventive engine builders incorporate this in their engine packages.