Grand Slam W-Series 1965 Chevrolet “409” Impala

Way back in the mid-1950s, Chevrolet was riding high with the debut of its small-block V8 engine. The new mouse motor was compact and powerful and could be easily modified for more grunt. But GM knew it had heavier cars and trucks on the drawing board and needed a bigger V8 to power this future portfolio. In 1958, Chevy’s W-Series big-block V8 was unleashed in the Impala, and “Rat Motor” took its place in the lexicon of automotive slang.

The W-Series Chevy big-block was named after its W-shaped valve covers, which were a result of its offset overhead valve design. The valves were not aligned with the center of the cylinder bore, but rather angled towards the center of the engine. This created a wedge-shaped combustion chamber between the piston crown and the cylinder head deck, instead of the conventional chamber in the head. The spark plugs were inserted vertically into the quench area of the chamber, which improved the flame propagation and reduced the risk of detonation.

The W-Series engine had a cast iron block with 4.84-inch bore centers, two-bolt main bearing caps, and a side-oiling lubrication system. The cylinder heads were also made of cast iron and had two valves per cylinder, operated by tubular steel pushrods and stud-mounted rocker arms. The intake and exhaust manifolds were attached to the heads by four bolts each, and the exhaust ports were siamesed between adjacent cylinders.

The W-Series engine had three displacement options: 348, 409, and 427 cubic inches. The bore and stroke varied depending on the displacement, as shown:

W-Series Displacement

Displacement Bore Stroke
348 cubic-inches 4.125 in. 3.25 in.
409 cubic-inches 4.3125 in. 3.5 in.
427 cubic-inches 4.3125 in. 3.65 in.

The power output of the W-Series engine ranged from 250 to 430 horsepower, depending on the compression ratio, carburetion, and camshaft. The most famous version was the 409-horse, dual-quad 409, which had two four-barrel carburetors, a solid lifter camshaft, and an 11.0:1 compression ratio. This engine was immortalized in the Beach Boys song “409”, which cemented its legendary status.

The W-Series engine was used in Chevrolet passenger cars and light trucks from 1958 to 1965. Some of the models that featured this engine were the Impala, Bel Air, Biscayne, Corvette, El Camino, and Suburban. The engine was also used in some racing applications, such as the Z11 Impala and the Mystery Motor, which were modified versions of the 409 and 427 engines, respectively. The W-Series engine was known for its high torque and low-end power, which made it suitable for drag racing and street cruising.

The W-Series engine was superseded by the Mark IV engine in 1965, which had a more conventional wedge-shaped combustion chamber and valve arrangement. The Mark IV engine was the basis for the later generations of the Chevy big-block engine. However, the W-Series engine still has a loyal fan base and is considered a classic and collectible engine by many enthusiasts. There are also some aftermarket parts and blocks available for the W-Series engine, which allow for more performance and customization.

This brings us to our feature car, Mark Smith’s 1965 Impala SS, which was the last year for a factory-installed 409 mill. This is a factory black-on-black car that has been lovingly restored.

Smith, hailing from Montoursville, Pennsylvania, owned the car for 13 years and it took him three years to restore it back to the glory you see here. Mike’s brother spotted it in a garage and thought it was complete and all there, it had rust in the floors, windshield header, and floors.  The rust was exorcised from the exoskeleton and then was treated to a full repaint by Ed Strobel and Matt Lance.

The old Chevrolet Impala is running a dual-quad 409 engine, good for over 400 horsepower. All that juice is sent to the rear via a four-speed manual, Hurst-shifted transmission. We love how Mike retained the stock look with the spinner caps, whitewalls, and factory stance. The bucket seat interior is stone-stock and that’s okay, as it will remain cool forever.

The Bill Mitchell fastback styling is timeless here and although it’s a huge car, the black seems to shrink it a size or two. From a design standpoint, 1965’s full-size cars represented the full transition to GM Design leader Bill Mitchell’s vision of car styling, and from the Impala all the way up to Cadillac, each division was tailored to a fresh new look.

Complete with that forward-thinking styling blended with iconic W-Series power, Mike’s 1965 Impala bridges both generations beautifully. Perhaps that is why this generation of the Chevy Impala is such a fan favorite. No matter what it is exactly that draws the affection of Bowtie enthusiasts to these cars, we think you’ll agree that Mike’s ride has it in spades. And that is exactly why we like it so much.

About the author

Dave Cruikshank

Dave Cruikshank is a lifelong car enthusiast and an editor at Power Automedia. He digs all flavors of automobiles, from classic cars to modern EVs. Dave loves music, design, tech, current events, and fitness.
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