Engine Balancing - Engine Builder Magazine

Engine Balancing

In the dark ages of the automotive industry, engine balancing was considered an art practiced exclusively by performance engine builders. Only those wizards of speed (it was widely believed) could understand the forces that caused drivetrain vibration – and more importantly, those that stopped it. Those few who could balance an engine were looked upon with admiration and awe.

Of course, in today’s enlightened world, it’s clear that balancing is beneficial to ALL rebuilt engines – and is often a necessary part of the process if you and your customers expect the engine to provide trouble-free service.

“In performance, balancing was always important. But with standard automobiles, balancing never used to be a factor,” explains Randy Neal, CWT Industries. “Now, through better manufacturing processes – including balancing — the OEMs have tried to reduce any force that causes wear. As a result, we’re seeing engines that go 100,000 miles instead of 50,000 miles.”

Neal points out that more precision at the OE level means a smoother running, longer lasting car, which we have all come to expect. The tradeoff comes at the rebuilding level, when you are required to not only meet the boring, alignment and surface finish needs of the engine but the balance as well. If standard engine rebuilders, who may not be used to thinking about performance and balance, don’t pay attention to the weight differences between parts, they could be setting an engine up to be a real shaker.

“When we introduce aftermarket components into the engine, in all probability we vary the balance,” says Neal. “There are wide variations in the parts manufacturing process. Even parts that are physically identical can have significant differences in weight. Mixing and matching connecting rods to make a set – even if they are all the same part number – may very well introduce a variation into the engine that will cause an unbalance.

“It’s critical that we as quality aftermarket suppliers build the equivalent of OE quality or better,” Neal says. “To do less is to undermine the industry in which we work.”


A smooth running engine isn’t just a nice thing to have – it translates directly into power. If the crankshaft, connecting rods and pistons aren’t tying to tear each other apart and in the process shake the vehicle to pieces, more power will be transferred to where it’s needed: the wheels.

Failure to balance the components properly can result in many different problems: piston rings failing to seal; main and rod bearing wearing early or irregularly; harmonic balancer deterioration; valve spring failures; timing chains stretching; bolts and fasteners working loose.

Don’t ignore comfort, though: fewer vibrations also mean accessories will last longer, and the vehicle will be more comfortable to drive.

“Think of the mom waiting to pick her kids up from school. Sitting there with a cup of coffee while the van is idling,” explains Tim Meara, Sunnen Products. “It’s not performance, – she may not be turning 6,500 rpms going down the highway, but if the rebuilt engine isn’t smooth and that coffee starts splashing across the dashboard, even she’ll know there’s a balance problem.”

Babcox Technical Editor Larry Carley explains that understanding engine balancing is actually quite simple – well, as simple as high school physics. “As everybody knows, a rotating object generates ‘centripetal force,’ which is an actual force or load generated perpendicular to the direction of rotation. Tie a rope to a brick and twirl it around and you’ll feel the pull of centripetal force generated by the unbalanced weight of the brick. The faster you spin it, the harder it pulls,” he explains.

“Centripetal force should not be confused with ‘centrifugal’ force, which is the tendency of an object to continue in a straight trajectory when released while rotating,” says the professor. “Let go of the rope while you’re twirling the brick and the brick will fly off in a straight line.

“As long as the amount of centripetal force is offset by an equal force in the opposite direction, an object will rotate with no vibration. Tie a brick on each end of a yardstick and you can twirl it like a baton because the weight of one brick balances the other,” says Carley.

A crankshaft is a heavy rotating object. What’s more, the piston and rod assemblies reciprocating back and forth along its axis greatly complicate the problem of keeping everything in balance.

“With inline four and six cylinder engines, and flat horizontally opposed fours and sixes (like Porsche and Subaru), all pistons move back and forth in the same plane and are typically phased 180

You May Also Like

NMRA/NMCA Announce Augustine Herrera as National Tech Director

ProMedia Events and Publishing, the parent company of the Holley NMRA Ford Nationals and NMCA Muscle Car Nationals, has announced Augustine Herrera as the new NMRA/NMCA National Tech Director. His duties include overseeing fair competition in both drag racing series and leading the on-site tech staff at all national events.  “Augustine joined our team in

ProMedia Events and Publishing, the parent company of the Holley NMRA Ford Nationals and NMCA Muscle Car Nationals, has announced Augustine Herrera as the new NMRA/NMCA National Tech Director. His duties include overseeing fair competition in both drag racing series and leading the on-site tech staff at all national events. 

Shop Solutions November 2021

Check out these Shop Solutions from builders across the country!

Cam Center
Holley Classic Truck Battery Tray and Hold Down

Holley Classic Trucks can battery trays for 1981-1987 C/K Series trucks and Blazer/Jimmy/Suburban manufactured to precisely mimic the factory look with all of the original holes and contours. Related Articles – Rocker Arm Tech – Part 1 – Automotive Specialty-Equipment Retail Sales Reach New High – Rebuilders Choice Made from heavy-gauge steel and EDP coated

Holley Battery Tray
Rocker Arm Tech – Part 1

In this episode of Steve Tech, Steve Morris breaks down the fundamentals of rocker arms, rocker arm stands and valvetrain rocker arm geometry. Class is in session! Related Articles – The SCAT Story – Numbers Don’t Tell The Whole Story – Performance Rocker Arms

Automotive Specialty-Equipment Retail Sales Reach New High

Despite what occurred throughout 2020, the specialty-equipment industry showed resilience with industry retail sales climbing from $46.2 billion to a new high of $47.89 billion in the U.S., according to the new 2021 SEMA Market Report. Related Articles – Future of Engine Building: Converting the Masses – Future of Engine Building: The Road Ahead for

Other Posts

COMP Performance Group Announces Plans for 2013 Power Tour

The Power Tour is considered one of the biggest and best road trips in the nation for performance enthusiasts. A variety of special events are scheduled throughout the week, including a highly anticipated cruise night in downtown Memphis (home of CPG) on the Tuesday, June 4. Related Articles – New AETC Website Debuts – PRW

New AETC Website Debuts

Each year AETCbrings together engine builders, racers, engineers and media members from around the world to exchange information on the day’s most popular engine-building topics. In an effort to make information about the conference even more accessible, AETChas recently launched an updated, easy-to-navigate website. Related Articles – Eaton Sponsors Western Michigan University Student Race Car

PRW Opens New Corporate Office and Warehouse Distribution Center

The PRW warehouse distribution center and corporate headquarters in now located in Perris, California. In addition to being designed to maximize storage and order shipping, the facility has an abundance of office space that houses the sales, management and support teams, an employee break room, conference rooms, and a larger engineering and product development department.

Melling, Dura-Bond Consolidate Sales and Marketing Efforts

Charles Barnett, vice president of sales and marketing at Dura-Bond Bearing Co., will be heading up the consoliated efforts between Dura-Bond and Melling. Barnett has been a long-term employee at the company as president prior to the Melling purchase several years ago. He also had a career with ACDelco/General Motors and previously served as general sales