Shelby-modified 289 High Performance V8 (1965–1967)
The solid-lifter Ford small-block tuned by Shelby American for the original GT350.
Overview
The original Shelby GT350 used a modified version of Ford’s 289-cubic-inch High Performance V8, commonly identified by the K engine code in regular Mustangs. The compact small-block combined high-compression pistons, a mechanical-lifter camshaft and strengthened internal components with the freer-breathing equipment fitted by Shelby American.
Ford rated the standard K-code 289 at 271 horsepower. Shelby added an aluminium high-rise intake manifold, a larger Holley four-barrel carburettor, tubular Tri-Y exhaust headers and a less restrictive exhaust system. These changes raised the GT350 road engine’s advertised output to 306 horsepower.
Architecture
The 289 was a 90-degree overhead-valve V8 with a cast-iron block and cylinder heads. Its 4.00-inch bore and 2.87-inch stroke produced 289 cubic inches, or approximately 4.7 litres. A relatively short stroke and solid valve lifters suited sustained operation at higher engine speeds than Ford’s ordinary small-block applications.
The High Performance foundation also used heavy-duty connecting rods, upgraded bearing caps and a counterweighted crankshaft. Shelby supplemented it with an enlarged oil sump to support hard cornering and extended competition use.
GT350 application
The engine was paired with a four-speed manual transmission in the 1965 GT350. Road cars used a single four-barrel carburettor, while the competition GT350R received further preparation that varied with team and race requirements.
Shelby retained the 289 through the 1967 GT350 model year as the Mustang body became heavier and more comprehensively equipped. A 302-cubic-inch small-block replaced it for 1968, ending the original 289-powered phase of the GT350.
Key specifications
- Configuration: 90-degree, naturally aspirated overhead-valve V8
- Displacement: 289 cu in (approximately 4.7 litres)
- Bore × stroke: 4.00 × 2.87 in
- Induction: Holley four-barrel carburettor on an aluminium high-rise intake
- Valve gear: Pushrod-operated overhead valves with mechanical lifters
- Compression ratio: 10.5:1
- Advertised output: 306 hp at 6,000 rpm
- Advertised torque: 329 lb-ft at 4,200 rpm
- GT350 application: 1965–1967