The Harmonic Balancer found on all 1979-1995 pushrod engines is integral to making sure your engine runs properly. Follow along, and we will cover everything you need to know on this subject!
Every internal combustion engine is equipped with three major components, pistons, connecting rods, and the crankshaft. This rotating assembly experiences a plethora of stress every time each cylinder fires. A harmonic balancer is also known as a vibration dampener or a crankshaft damper and is attached to the free end of the crankshaft. This part is vital to prolonging your high-performance engine's life and overall durability.
The harmonic balancer serves many purposes for your engine. The primary function of a harmonic balancer is to dampen harmonics and torsional vibrations produced during the combustion cycle. The balancer is press-fit to the crank to ensure these parts operate efficiently together. The engine vibration can wobble or shake itself apart without this in place. The balancer also serves as the primary connection point for the front-end accessory drive. A crank pulley connected to the balancer then turns other engine parts by a serpentine belt like your alternator, water pump, and even superchargers. Timing marks are also etched or cast on the body to help set ignition timing.
One of the biggest questions in the Ford Mustang community is what size harmonic balancer do I need? Whether the crankshaft is internally or externally balanced will determine the size or oz you need. An internally balanced application will have all counterweights located on the crank itself. In this case, the harmonic balancer and your flywheel/flexplate will be a neutral or 0oz balance.
Externally balanced engines use the harmonic balancer and your flywheel/flexplate as a weighted counterbalance. This is where the 28oz and 50oz options come into play. Depending on your engine builder, your build could go either way. Engine components can vary from build to build and manufacture specifications. All three of these parts must match. Overall engine performance, engine harmonics, and longevity will suffer, or even a catastrophic failure can result in mismatched parts.
Ford produced 5.0 (302) and 5.8L (351) with an externally balanced engine from the factory. All OEM 5.0L 302 applications featured a 50oz harmonic balancer, and the 5.8L 351's used a 28oz balance. Since these are externally balanced, the 0oz harmonic balancer is not utilized for factory applications. Some aftermarket manufacturers' specifications can call for these three sizes to be used. Aftermarket stroker kits in the Ford community for late model Mustangs commonly use either a 28oz or 0oz balance in most cases.
Many different symptoms can arise from a failing harmonic balancer. If these are prolonged and not resolved, engine failure can result. Below are some of the most common symptoms of a bad harmonic balancer.
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