Tech Feature: Balance Between Crankshaft and Related Components is Critical – UnderhoodService
Connect with us
Close Sidebar Panel Open Sidebar Panel

Engine

Tech Feature: Balance Between Crankshaft and Related Components is Critical

Balancing used to be the exclusive domain of the performance engine. Stock grocery getters rarely were considered candidates for balance jobs. But that thinking has changed. Even standard, run-of-the-mill automobiles are sent from the OE with precisely balanced engines. And customers have come to expect nothing but the same when they look into having their vehicle’s engine rebuilt.

Advertisement

By Doug Kaufman
Editor
ENGINE BUILDER

Click Here to Read More
Advertisement

Everyone is looking for balance in their lives – balance between work and family, between responsibility and recreation, between give and take. Too much of one at the expense of the other can lead to dire consequences.

The same thing can be said about the engines you rebuild. Balance between the crankshaft and its related components is critical to providing a smooth, trouble-free powerplant.
Balancing, once considered an art, has turned into a science. New equipment and technology have made balancing accessible to most engine builders. Though it can seem to be a confusing topic, new equipment takes the guesswork out of the process and can help nearly anyone quickly and easily balance an engine.
“A smoothly running engine isn’t on anybody’s ‘wish list’ anymore,” explained one veteran of the balancing wars. “It’s demanded. And it has to do with more than just comfort. If the crank, rods and pistons are working together and not trying to shake the engine to pieces, there will be more power transferred to where it’s really needed.”

Balancing used to be the exclusive domain of the performance engine. Stock grocery getters rarely were considered candidates for balance jobs. But that thinking has changed. Even standard, run-of-the-mill automobiles are sent from the OE with precisely balanced engines. And customers have come to expect nothing but the same when they look into having their vehicle’s engine rebuilt.

Advertisement

With “internally balanced” engines, the counterweights themselves handle the job of offsetting the reciprocating mass of the pistons and rods. “Externally balanced” engines, on the other hand, have additional counterweights on the flywheel and/or harmonic damper to assist the crankshaft in maintaining balance. Some engines have to be externally balanced because there isn’t enough clearance inside the crankcase to handle counterweights of sufficient size to balance the engine. This is true of engines with longer strokes and/or large displacements.

Balancing, once considered an art, has turned into a science. New equipment and technology have made balancing accessible to most engine builders. Though it can seem to be a confusing topic, new equipment takes the guesswork out of the process and can help nearly anyone quickly and easily balance an engine. But with the advent of this technology, has the need for balancing been lessened? Have we reached the point where “close enough” is “good enough?” Leading suppliers of balancing equipment say “absolutely not.” In fact, the need has only gotten more pronounced.

Advertisement

Demand for balancing isn’t just seen in the performance and racing community, says Jim Davis of Fentech Co. “With higher rpms in performance engines and longer life in drivetrain components in commercial vehicles, balancing plays a role in the longevity of engine life. It is important to balance to a higher quality standard, just as other tolerances have become more stringent.”

Michael Turner, Turner Technology, says he believes the need is greater than ever, but so is the awareness. “The importance of balancing is being stressed more, because people have learned over the years how bearing and component life is improved because of it. There was a time when we tried to ‘cheap out,’ to get the jobs, but now engine builders are more likely to push the facts to their customers that ‘you really need to do this when we change the parts because it WILL affect the reliability and longevity of your engine.’”

Advertisement

CWT Industries’ Randy Neal says parts proliferation has impacted the need for balancing. “Balancing services have radically increased over the last few years. The increase of aftermarket crankshafts and related components has set off a series of events forcing all rotating assemblies to be suspect. Even though the end user may order from one supplier, that supplier probably uses multiple sources for the individual components. The issue here is that there is no mechanism in the parts chain to insure that all parts match. At the end of the day, there’s a high probability that the components are NOT matched, and this forces the rotating assembly to be balanced,” he says.

Advertisement

“The single biggest reason that balancing is more necessary than ever,” agrees Hines Industries’ John Witt, “is the availability of performance parts on the Internet. This is in conjunction with the availability of stroker kits that increases rather than eliminates the need for balancing.”

Turner recalls a time when people could change some components, maybe upgrade the pistons with similar but not radically different styles, and not change the balance much. Those days are over. “What you could get away with 10 years ago, you just can’t anymore. The other guy is looking for every advantage he can get, too. You’d better throw everything you can at it now, or you’re just going to lose and waste all your money anyway.”

Advertisement

Neal acknowledges that stroker parts continue to require balancing. “Common sense tells you that a stroker kit changes the rotating mass with longer throws. This forces the crank manufacturer to offset the counterweights and, generally, the rod length or pistons have also been modified. At this point, the bobweight has been modified and the result of these events mandates that the unit be balanced.

“Even though we’ve heard claims from some suppliers that all of their components are within balance standards, as of this date, I’ve never seen a purchased performance kit assembly balanced to within racing standards (.2 oz.in.). Most exceed 2 oz.in, and that is the minimum standard for OE manufacturers. Remember, these standards are not equal to the requirements of a high-performance engine,” Neal explains.

Advertisement

While many suppliers do offer a balanced assembly, says Fentech’s Davis, depending on the supplier and the parts offered, the term “balanced” may be up for discussion. “A stroker should still be balanced, just like any other crank assembly.”

Davis says adding heavy metal is often required, but whether it is or not, almost all crankshafts can be balanced. “I have heard on occasion from customers that counterweights were not positioned properly and the crank couldn’t be balanced, but that is rarely the case. Other items that should be checked that can cause difficulty in balancing include a bent crank, improperly ground journals or a cracked crankshaft.”

Advertisement

The process of balancing begins by weight matching the individual parts including pistons, rods and rings. Bobweights are added to the crankshaft to simulate the reciprocating weight of the piston and rod assemblies and then the crank is placed in the balancer.

The crankshaft is spun to determine the points where metal needs to be added or removed from the counterweights. If the crank is heavy, metal is removed by drilling or grinding the counterweights. If the crank is too light, Mallory metal (a special very heavy metal) is added by drilling holes into the counterweight and adding Mallory as needed.

Advertisement

Says Randy Neal, “In general terms, I don’t believe there is any manufacturer that produces a bad crankshaft. The challenge for all crank manufacturers is for them to have specific knowledge of the application and customize the crankshaft design to meet these requirements. In almost every application that I have been associated with, the bobweight that is used by the end-user is not equal to the target weight that the crank manufacturer used.”

This is why, says Gary Hildreth from GH Balancer Service, a builder’s best bet is to choose parts with a good reputation. “Kits should always be checked,” he says. “Each different supplier has its own quality standards and the rebuilder will find those reliable sources after they check the work. Some cranks always need to be reground, for instance, before they’re balanced. Again, buy good merchandise from good vendors.”

Advertisement

Should you take the word of the supplier when it comes to balanced components? John Witt says the end user has the choice. “The real question is, if you opt to have the kit provider perform the balancing service, what are the tolerances the components will be balanced to?” he asks.

“My recommendation would be don’t order parts as a balanced assembly,” says Turner. “You’ll be checking all the parts against the specs anyway. Do it yourself, balance it yourself because you know you’ll take more time and pay more attention to the detail. When you do it yourself you know it will be done right”

Advertisement

In fact, Turner suggests that anyone who builds engines should have a balancer for this simple reason: You’ll do the job right. Plus, anytime you sub out the work, you have a chance to lose business.

“One of my customers told me ‘I used to sub out my balancing work. After a while, the people I was planing the heads for, doing the valve jobs for and handling all the other problems for, started using my balancing guy for all the work.’ That really opened my eyes,” he says. “People like to shop in one place and if they have to drop things off here, pick things up there, the guy who has the balancer suddenly finds himself picking up a lot of the other work they used to take to other places.”

Advertisement

The experts with whom we’ve discussed this topic agree: balancing may be mysterious to the neophyte, but it is certainly within the scope of today’s shop owner.

“A lot of the old timers mistrust the computers found in today’s balancers,” says Gary Thompson of ABS Products. “They often want to have a test piece to prove to themselves that what they see on the screens is correct. Make no mistake – there’s some real nice new equipment out there. It’s just there’s a different learning curve for the experienced guys.”

Advertisement

Gary Hildreth agrees: “The computerized equipment is easier to use than ever. The younger you are, the faster it goes, but everyone can learn how to use them.”

The latest technological enhancements in balancing include extremely sophisticated software and very sensitive transducers. These make balancers faster than ever and easier to use, enough so that shop owners can save time and increase their profitability. “With the software available today,” says Davis, “a technician can be balancing a crank in a matter of a couple of hours of use with the machine. With items such as drill calculators and heavy metal correction features, these items take a lot of the guess work out of balancing.”

Advertisement

Witt explains it this way: “I always ask them if they can use an ATM. If so, the new balancers require just about the same amount of information to set up a new work piece as performing a typical ATM transaction at your bank. That’s, of course, if you haven’t stored the parameters from a previous job. If you have, then it’s only a push of a button and you are ready to spin the crank and take a measurement.”

Randy Neal says the learning curve to using today’s balancers can be subjective. “Can experienced technicians easily make the jump to computerized equipment? That all depends on the system being used. Simply put, not all computerized equipment is the same. The operating and software system that we use is intuitive and directs the technician to the perfect solution with minimal knowledge. We feel we’ve led the way with simplicity with user-friendly software but at the same time we continue to refine the method for handling unusual balancing challenges.”

Advertisement

What is apparent is that while the basics of balancing have remained the same over the years, the market’s needs and the technology have changed dramatically. Neal suggests that every two years significant changes are seen in this industry. Are your skills and your equipment balanced and up to the challenge?

Advertisement
Click to comment
Connect
UnderhoodService