820 CID EFI Marine Engine - Engine Builder Magazine
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Engine of the Week

820 CID EFI Marine Engine

Known for 700ci to 1,000ci engines, Sonny’s Racing Engines understands how to make big power for many applications. This 820ci EFI marine engine puts out a whopping 1,450 hp for some serious fun on the open water.


Most rebuilders in this industry have been forced to become a jack-of-all-trades, taking in any job that walks through your doors. Sonny Leonard, president and CEO of Sonny’s Racing Engines, is no different. However, the engine shop he started in 1969 in Lynchburg, VA, is known for 700cid to 1,000cid engines for drag racing, truck pulling, extreme muscle car, and boat applications. The shop also sells engine components to other engine builders.

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Sonny’s has 16 employees with 10 of them having been with the company for over 20 years. Sonny’s also designs and manufactures its own cylinder heads and machines them in-house with 5-axis CNC machines. One of the engines that Sonny’s recently built is an 820cid EFI marine engine with hemispherical heads.

“The 820cid EFI marine engine uses our newly designed 5.300˝ bore spacing hemispherical cylinder heads,” Leonard says. “820cid is 5.045˝ bore by 5.125˝ stroke. Other engine components are a Bryant racing steel billet crankshaft, CP-Carrillo steel billet rods, Diamond pistons, and a 70mm tool steel endurance cam from COMP Cams.”

Sonny’s also used a multi-layer head gasket designed for naturally aspirated and forced induction by Cometic Gasket. In addition, the EFI marine engine gets Jesel keyed lifters and a CN billet aluminum block with 360-degree water jackets exclusively for Sonny’s.

“We use the very best components to complete our engines,” he says. “The uniqueness of this engine is that it is designed for endurance boat applications versus how our drag racing and NTPA truck pulling engines would perform.”

To test that performance, Sonny’s has two superflow dynamometers. The 820cid engine will operate on 89 to 92 octane unleaded gas. This engine puts out 1350 lb.-ft. of torque at 5,600 rpm and 1,450 hp at 6,400 rpm.


Sonny’s also offers a 2017 stage II version, which uses a billet intake manifold, front mounted throttle bodies and a billet oil pan with 5 stage billet oil pump.

“What makes our engines successful are our employees who take pride in their work, and good work ethics,” Leonard says. “My philosophy on having a well-known company is your employees have to be as good or better than you in all positions.”


Sticking to that philosophy is what makes this one marine engine ready to hit the open water.

The Engine of the Week eNewsletter is sponsored by Cometic Gasket.

If you have an engine you would like to highlight in this series, please email Engine Builder magazine’s managing editor, Greg Jones at [email protected]

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