Ford Boss 302 V8 (1969–1970)
The high-revving five-litre small-block developed to support Ford's Trans-Am racing programme.
Overview
Ford created the Boss 302 engine to give the Mustang a competitive five-litre foundation for the Sports Car Club of America’s Trans-American Sedan Championship. It combined the compact dimensions and short stroke of the Windsor small-block with large-port, canted-valve cylinder heads derived from the new Cleveland engine family.
The resulting road engine displaced 302 cubic inches and was advertised at 290 horsepower. Its solid-lifter valve gear, large four-barrel carburettor and free-breathing heads favoured higher engine speeds, giving the Boss 302 a different character from the larger, more torque-focused V8s available in other Mustangs.
Architecture
The cast-iron block used a 4.00-inch bore and 3.00-inch stroke. Four-bolt main bearing caps, a forged-steel crankshaft, heavy-duty connecting rods and forged pistons strengthened the rotating assembly. Screw-in rocker studs and adjustable valve gear supported the mechanical camshaft.
The canted valves and generous ports allowed strong airflow, although their size also reduced mixture speed at low revolutions. Ford revised details of the cylinder heads and valve sizes between the 1969 and 1970 production engines while retaining the same basic architecture and advertised output.
Road and competition use
The production Boss 302 paired the engine with a four-speed manual transmission. A rev limiter protected the road engine, while the Mustang also received competition suspension, quicker steering and front disc brakes to make use of its high-speed performance.
Trans-Am racing engines were prepared beyond showroom specification, but the production engine and car supplied the homologation basis required for competition. Bud Moore’s factory-supported Mustangs secured the 1970 manufacturers’ championship, fulfilling the purpose behind the Boss 302 programme.
Key specifications
- Configuration: 90-degree, naturally aspirated overhead-valve V8
- Displacement: 302 cu in (approximately 4.9 litres)
- Bore × stroke: 4.00 × 3.00 in
- Induction: Holley four-barrel carburettor
- Valve gear: Pushrod-operated overhead valves with mechanical lifters
- Compression ratio: 10.5:1
- Advertised output: 290 hp at 5,800 rpm
- Advertised torque: 290 lb-ft at 4,300 rpm
- Boss 302 application: 1969–1970