CAMSHAFT ­BALANCING (Part 1)

CAMSHAFT ­BALANCING

That’s right, camshaft balancing. It’s all about optimizing and regaining lost energy.

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The camshaft is yet another rotating mass, so why would we not pay attention to the subject of balance?

When was the last time you balanced a camshaft? If you’re like most builders, the answer is never, with the answer accompanied by a puzzled look. Immediately following that answer, most folks are likely to add, “And why the hell would we want to?” At the outset of a recent conversation with equipment-innovation guru Randy Neal of CWT Industries in Norcross, Ga., I have to admit that I had much the same reaction. Neal has developed a software program for balancing camshafts, and after about 10 minutes of listening to his theory, I became a believer.

Once you’re able to erase any long-standing notions and establish an open mind, it makes perfect sense. After all, balance is key in any rotating mass, and cams are no exception. Just consider all of the components that are currently considered candidates for balance checking and balance correction: crankshafts, drive shafts, propeller shafts, supercharger shafts, armatures, turbo impeller shaft assemblies, ring gears, wheels, flywheels, transmission shafts, etc. Why then would we blindly ignore camshaft balance? Just because it’s never been addressed in the past doesn’t mean that it isn’t a good idea. It’s called progress and taking advantage of technology. It wasn’t that long ago that most folks didn’t see the need or benefit of engine coatings. Today, taking advantage of thermal barrier, anti-friction and oil-shedding coatings is commonplace, with proven results.

FINDING BALANCE

Yes, some would argue that since the cam runs at half the speed of the crank, camshaft balance isn’t an issue worth exploring. With all due respect, I disagree. While an out-of-balance camshaft may not create a vibration that will be felt in the seat of the pants, any out-of-center forces can create a harmonic disturbance, and that disturbance, or excitement, can result in frequency disturbances (OK, vibrations) that can be transmitted through the rest of the valvetrain, including lifters, pushrods, rockers, springs and valves.

If you wish, you can view the camshaft as a tuning fork. An imbalance condition can excite the cam. Correcting the imbalance can mute or eliminate the excitement. Some might say that an camshaft imbalance would be absorbed by the valve springs, but this is exactly the point-why introduce more vibration or unwanted frequencies into the valve springs if it can be avoided? The springs already have enough work to do. Balancing the camshaft may very well “calm” the springs, removing unnecessary distractions, allowing them to concentrate on the job at hand, which is controlling the valves.

We’re not talking about reinventing the wheel here. Rather, we’re talking about making the engine perform at the best of its abilities. When you’re building a high-performance engine and your goal is to optimize engine performance, it just makes sense to include camshaft balance as part of the overall equation. Will balance correction make more horsepower? No. However, correcting an imbalance condition of any rotating engine component is a positive step toward reducing vibration, uneven loading and unwanted harmonics, which can, in turn, free up horsepower. There’s a difference.

Creating balance or, more accurately, reducing or eliminating imbalance, will reduce the negative effects of lost energy, allowing the engine package to function more efficiently. And nobody can argue that increased efficiency will allow the engine assembly to function at its peak potential, both in terms of power and durability.

NOT ALL BALANCE PROBLEMS ARE THE SAME

At this point, I think it’s best to include information obtained directly from Randy Neal. According to Neal, virtually every camshaft made is not balanced. “We have tested hundreds of camshafts and have never found one that was balanced,” he said. “As a matter of fact, we rarely see two camshafts with the same profile that have exactly the same unbalance. Now you may be saying that just can’t be true due to the accuracy of the new CNC cam grinders; but the balance problem does not generally come from the grinding operation. Rather, it actually started with the raw casting or forging.”

“When the camshaft blanks are made they have Center Registers placed at each end of the camshaft,” Neal continued. “The main bearing and base circle of each lobe are established from these registers. The axis of rotation and the Center of Mass is probably not the same. In fact this is generally what forces that camshaft to be out of balance. It’s important to understand that when the Center of Mass is not the same as the Center of Rotation, there will be a balance error.”

“When a camshaft is out of balance, we need to know the amount of unbalanced forces and their location relative to each other,” Neal said. Pictured are visual reports of a 60mm Roller Camshaft that has been inspected on a Computerized Balancing Machine.

The ultimate result is that the engine will not perform as intended. In all probability at an unknown moment, at an undetermined rpm, the engine will make less power. Neal also noted that, “We have seen this on the power curves when plotting the horsepower/torque on the dynamometers. Some engine builders have determined that these anomalies can be related to ignition/fuel and/or flow characteristics of poorly designed intake systems, and they could be right.”

“However, when the intake system is modified and the same rpm related anomaly is re-plotted, there is strong evidence that the valve train is the potential cause and the vibration of the camshaft has the ability to cause these results,” Neal said.
In all fairness, balancing the camshaft may not eliminate all or any of the valve train issues due to the fact that there are several other moving objects that may have natural frequency issues that could become excited from surface speed activities (rocker flutter, valve spring float, push rod deformation and excess end-gap clearances). But by balancing the camshaft you have eliminated a known variable that will not be a part of your quest for the ultimate performance of your engine.

For the skeptics out there who still believe that the camshaft harmonics have no relevance to horsepower gains, I agree that it will not make power. Rather, it simply unleashes it. There is no discussion that can be supported that says balancing any rotating mass will cause any object to perform in a negative manner.

HOW CAMSHAFT IMBALANCE IS CORRECTED

Correcting the unbalanced camshaft can be achieved by several methods. The first is to modify the timing gear by removing or adding material as specified by the balancing machine. The second is to remove weight from the core of the main bearing area or add weight by first drilling holes into the main bearing and replacing it with heavy metal.

Another option is to drill holes in the butt of the cam and possibly add heavy metal, or to add external weight to the shaft itself. This can be achieved by using an adaptor that is added to the rear of that shaft which locates a counter weight that is modified for the require amount to balance the assembly, or, given the cam design and spacing between lobes, clamp-on counterweights between cam journals.

Is camshaft balancing a necessity? For the street car? No. For the race car? Yes, assuming that your intent is to optimize the engine in order to extract all of its potential. It’s just one additional small step forward for the racer. And that’s a good thing.

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  • Alex

    It’s interesting to note that this article talks about that this is a requirement for racing / performance engines, I agree. Although, where I disagree is that street cars don’t need this. I believe this is an incorrect assumption.

    Whereas, it’s true, if an engine or mechanical system is balanced completely you do retrieve lost power. This is very much necessary when it comes to tweaking and tuning for fuel efficiency. If everything is balanced in the engine, you will have more available horsepower and torque even when you’re having more restrictive valve timings in regards to fuel efficiency over power.

    Without the precision balancing of a mechanical system, in this case engine, you will get the fuel economy but you don’t get full advantage of a well balanced engine put under the same timings. In other words you have more headroom in terms of horsepower and torque than you do without it.

    A good example is the Japanese import tuners, you can take a Honda CRX turbo and further balance the engine so you free up more horsepower but at no cost to the fuel economy, in some cases, you get better fuel economy because the engine and it’s components are not fighting each other. So, effectively you can gain in three areas by doing such.

    The third area is durability, if you use quality pre-precision balanced components your engine and all the components inside the assembly will last a lot longer. The ROI is a longer lower curve but comparing it to the sharp peaks of costs associated to using OEM parts that are not precision balanced items, it’s actually a lot lower. Using items that aren’t precision tuned is asking for trouble, not only do you have a loss in horsepower and torque, fuel economy but you have a shorter life of unbalanced parts and ultimately the entire assembly (engine) has a shorter life because of this fact.

    It’s interesting to note, to take an engine that has electronic valve timing and then try to remove the EVT, to run it as a normal engine, it has horrendous problems and you will notice the engine isn’t mechanically balanced from the onset.

    The irony of this situation is that I am an Electronic Engineer but I don’t like electronics covering bad mechanical operations and/or design. EVT should be an additional option for more performance rather than a requirement for operation.

    Above all, I love mechanical excellence, next comes electrical and electronic excellence, then the marriage between the two. That’s what turns my crank (mechanical pun intended). Although, I have to admit, I love the classic cars without all the complex electronics equally as much. It’s all about the commitment to quality and pride in your work.