SEMA 2021: SCAT Cranking Out Power With Flat-Plane Crankshafts

Novelist Stephen King, the Master of Horror, once said, “Sooner or later, everything old is new again.” In a planar view of things, the flat-plane crankshaft is representative of King’s remark. GM engineers and Bowtie enthusiasts have been dropping the term “flat-plane crankshaft” frequently in the past year or so. This might lead you to believe this engineering marvel is new. SCAT’s Tom Leib knows differently. 

 

“We can make a flat-plane crank for anyone,” says Leib. “We’ve been making them for years. To us, it’s nothing new.” In fact, Leib explained, “Cadillac first used the flat-plane crank in 1915.” 

What’s It All About?

According to Leib, most people don’t understand what a flat-plane crank is all about. “The header guys talk about this all the time. On a standard V8 engine, it is impossible to have tuned headers with equal-length pipes because of the firing order,” he explained. “It fires, then at 90 degrees, then 180, 270, then 180 back to number one. So what happens is, the one with the short pipe gets there too soon and the one with the long pipe gets there too late. So there is never that rotation of equal pulses into the collector so you can use the exhaust for scavenging and jump-starting the intake.”

While it may sound inventive and complicated, it is actually a simple design. “In a common V8 cross-plane crank, you would start with the number one pin, pin two at 90-degrees, pin three at 180-degrees, and pin four would be at 270-degrees to the number one pin. This spaces everything equally around the centerline of the crankshaft,” says Leib. “A flat-plane crank is equally spaced around the centerline as well, but at 180-degree spacing instead of 90-degrees.”

Why Does This Matter? 

Leib breaks it down by saying the flat-plane crankshaft offers better cylinder head breathing symmetry and scavenging. “Because of the firing order on a flat-plane crank, when the exhaust comes out of the combustion chamber somewhere around 1,300-1,500 feet per second, it jump-starts the intake port to move. This jump-start makes the engine more efficient. A flat-plane crank doesn’t necessarily make more horsepower. Still, the torque curve flattens out for a more extended period because it breathes better, creating a more usable powerband. Plus, if you’re getting a more efficient fill of air in the cylinder, you will generate more horsepower with less fuel.

Ultimately, it is about efficiency. If you are interested in doing more with less, visit SCAT online at www.scatcrankshaft.com to find out more about SCAT’s line of flat-plane crankshafts.

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About the author

Bobby Kimbrough

Bobby grew up in the heart of Illinois, becoming an avid dirt track race fan which has developed into a life long passion. Taking a break from the Midwest dirt tracks to fight evil doers in the world, he completed a full 21 year career in the Marine Corps.
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