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SAR 940 Racing Engine - Beyond All Measure

Sonny's 940 Cubic-Inch Pump Gas Monster Gives Rise To A Whole New Genre.

By Rod Short, Photography by Rod Short

When it comes to making horsepower, the thought that bigger is better has driven the motorsports hobby for years. In the late 1950s, the first 348 ci big-block Chevrolet spawned an infamous family of engines ranging from the 409 in 1961, and then the 427 Mystery Motor two years later. With a 4.840-inch bore center and 9.800- to 10.200-inch deck height, the next generation of big-blocks opened the door for engines with displacements of 396, 454, 472 and 572 ci, which is at the top of the food chain for GM big-block crate engines.

Even so, the demand for greater horsepower continued to grow as stock Rat motors gave way to strokers, which in turn, stepped aside for a rash of mountain motors.

Starting at around 632 ci, cubic inch inflation began to push the limits of conventional thinking. Engine builders responded with aftermarket blocks with spread pan rails, revised cam locations and raised deck heights, but they began to hit a brick wall when it came to getting much more than 700 ci out of an engine block. Sonny's Automotive Racing (SAR) helped break that barrier years ago by developing stretched engine blocks with 4.900-, 5.000- and then 5.300-inch bore centers.

By stretching the block to provide a bigger combustion chamber, larger bore and broader power band while still maintaining optimal valvetrain geometry, a larger engine with a higher base power level would provide builders much more flexibility, no matter what kind of power adders they used. Spraying less nitrous would lead to blowing less gas past the exhaust valve, smaller turbos would give quicker spool up and smaller blowers would lead to less engine wear. With the greater range of choices that a bigger engine provides, crew chiefs in Pro Mod, Outlaw 10.5 and Top Sportsman suddenly had more options and flexibility in putting an engine combination together.

Today, the evolution of this engine species continues to evolve as SAR has released a new 940 ci monster motor that represents the top of the food chain in naturally aspirated engine technology (and price). Representing the top of the mountain in the 5.300 engine family, this new 940 engine, even in this pump gas configuration, provides a number of advantages over the smaller, but better known IHRA Pro Stock engines that have produced the quickest and fastest N/A quarter-mile doorslammers in the world.

"No matter whether it's F1, NASCAR or drag racing, the trend over the past few years have been to go with a larger bore and less stroke in order to move the power band up," said Sonny Leonard. "An 825 ci engine will typically use a 4.800-inch bore with a 5.700 stroke. Here, we're using what cleans up to a 5.080 bore with a 5.800 stroke. As a result, the engine is much easier on the rods, makes more power and actually costs less, too."

Of course, brute power is what any of the 5.300 family of monster motors is all about. Dyno tests on this particular engine showed a whopping 1,702 peak horsepower at 7,200 rpm with 1,357 lb-ft of torque at 6,000 rpm on 93 octane pump gas. By comparison, this is nearly 2.5 times the peak power of a 720hp ZZ572/720R crate engine. Figure to spend just under a hundred grand for the 940 in this article.

By Rod Short
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