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Design Your Own Engine? Inside Goodwin Competition’s Semi Hemi

Why build engines designed by someone else? 

With CAD, FEA, CFD and CNC software readily available to those with computer and engineering skills, it’s now possible to design a purpose-built racing engine and machine the major components in a well-equipped shop. That’s the strategy Todd Goodwin took when he saw a void in the premium high-horsepower markets of truck pullers and 5-second drag cars and designed an all-new foundation with 5.0-inch bore spacing.

Sharp-eyed readers will recognize this mountain motor from the EngineLabs50 Hottest SEMA Engines” gallery. It’s the Goodwin Competition Semi-Hemi, and at 650ci it’ll twist the dyno to the tune of 1,600 horsepower and 1,110 lb-ft peak torque. In a smaller 630ci marine configuration topped with twin Whipple superchargers, it’ll crank out nearly 1,800 horsepower at a steady 6,600 rpm.

Goodwin studied the pros and cons of existing mountain motors and knew where he could make improvements. 

The block and heads are machined from 6061 T6 billet aluminum.

“We tried to build it with every feature possible,” says Goodwin, noting that he was able to leverage experience from his company’s NASCAR development projects to improve different engine features. “We designed the block with thermodynamics in mind. We have strategic webs for strength and thermal properties.”

Again, a void in the market inspired the head design. 

The Goodwin Competition mountain motor is designed for truck pullers and Pro Mod/Comp style drag cars.

“If a hardcore Mopar guy wanted an engine for a puller or drag car, Dodge doesn’t make much for 5.0-inch bore spacing,” explains Goodwin. “We originally started out with something Dodge owners could relate to by making the spark plug angles like a Hemi 99. We then wanted to expand the market.”

Goodwin kept the basic foundation but continued to redesign the valvetrain geometry to eliminate all severe angles.

“The biggest key is valvetrain dynamics,” says Goodwin. “We have an in-house Spintron to make it reliable at high rpm. We also designed the rocker arms with long pivots, and our valve and pushrod angles are just about perfect with no offsets.”

Goodwin used Solid Works to design the engine and also performed finite element analysis (FEA) simulations to confirm durability. The block is CNC machined from 6061 T6 billet aluminum and features iron sleeves and 18 studs per head. The 2-inch raised, enclosed cam tunnel features nine journals and supports 70mm cams. The heads are also machined from billet. Both the block and heads have water jackets, although the water does not flow between the head and block through the decks. 

The current architecture will allow displacement up to 1,013ci.

“It just comes down to buyers and money,” says Goodwin.

The Goodwin Competition Semi Hemi was one of EngineLabs’ “50 Hottest Engines of SEMA.”

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About the author

Mike Magda

Mike Magda is a veteran automotive writer with credits in publications such as Racecar Engineering, Hot Rod, Engine Technology International, Motor Trend, Automobile, Automotive Testing Technology and Professional Motorsport World.
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