Throwback Thursday: Let’s Talk Engine Balance With SCAT Crankshafts

Can you believe the end of another week is fast approaching? That’s right, another Friday is about to land on our doorstep. Now that another Thursday has made its presence known, that means it’s time for another Throwback Thursday.

This week, we are taking a trip back to July 2018 to check out, Let’s Talk Engine Balancing With SCAT Crankshafts. Engine balance is one of those aspects of performance that many know about, but not many really understand the concept? To help you guys gain a clear understanding of the process, we reached out to Tom Leib of SCAT Crankshafts to get the skinny.

Heavy metal (Mallory), weighs twice that of regular steel. This makes it a great option for adding weight to a crankshaft. The counterweight is machined, and the piece of Mallory is pressed into the hole.

Balancing an engine is done by taking away or adding metal to the crankshaft counterweights. But, to find balance, you need to know bobweight. The bob weights are actual weights that are attached to a crankshaft’s rod journals when balancing to simulate the weight of the rod and piston assembly. With the bob weights in place, the crank is ready to be spun on a balancing machine. While there are simple formulas to calculate the amount of bobweight needed, in the original article, you’ll learn there is a lot that these calculations fail to consider.

Tom stated, “Not balancing your crankshaft is like herding ants. Everything inside the engine works together, and if you have cylinders fighting each other, you’ll have bad vibrations. It’ll shake everything apart.”

If weight is being removed, the crankshaft’s counterweight is either drilled or cut in order to lighten it. The counterweight can be drilled in specific spots, or the crankshaft can be turned on a lathe and the counterweight can be cut down to achieve balance. If turning the crankshaft on a lathe is possible, in a lot of ways, it is a better way to remove weight. Cutting removes mass, which changes inertia characteristics. Anytime overall rotational mass can be reduced, it’s beneficial. Unfortunately, this is not always an option. Many times, weight needs to be removed from a specific location.

Engine Balance

To balance this crankshaft, holes are drilled into the counterweights to either remove weight or, to be filled with heavy metal to add weight.

If you must add weight, A heavy metal needs to be added to the counterweights. This requires the counterweights to be drilled in specific locations, and pieces of Mallory be pressed into those holes. Mallory is Tungsten, which weighs roughly twice as much as steel. This allows engine builders to add very specific amounts of weight to exact locations to achieve balance.

The challenge with adding weight is that material needs to be removed before weight can be added. So, hypothetically, if 28 grams needs to be added, 14 grams will be removed in order to add 28. This gives you roughly a 14-gram increase in weight.

engine balance

There’s alot more in-depth insight into this informative article, and that definitely makes it worthy of a second look. For that reason, I selected Let’s Talk Engine Balancing With SCAT Crankshafts as this week’s Throwback Thursday showcase article.

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About the author

Randy Bolig

Randy Bolig has been working on cars and has been involved in the hobby ever since he bought his first car when he was only 14 years old. His passion for performance got him noticed by many locals, and he began helping them modify their vehicles.
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