Ford Boss 302 engine
|Ford Boss 302|
|Manufacturer||Ford Motor Company|
|Configuration||Naturally aspirated 90° V8|
|Displacement||302 cu in (4.9 L)|
|Cylinder bore||4 in (101.6 mm)|
|Piston stroke||3 in (76.2 mm)|
|Block material||Cast iron|
|Head material||Cast iron|
|Valvetrain||OHV 2 valves x cyl.|
|Fuel system||Holley Carburetor|
|Oil system||Wet sump|
|Power output||290 hp (216 kW) @ 5200 rpm|
|Specific power||59.2 hp (44.1 kW)/Liter|
|Torque output||290 lb⋅ft (393 N⋅m) @ 4300 rpm|
|Successor||Ford Boss 351 V8|
The Ford Boss 302 is a high-performance "small block" 302 cu in (4.9 L) V8 engine manufactured by Ford Motor Company. The original version of this engine was used in the 1969 and 1970 Boss 302 Mustangs and Cougar Eliminators and was constructed by attaching heads designed for the planned 351 Cleveland (which debuted the following year) to a Ford small block. The construction was aided by the two engines sharing a cylinder head bolt pattern, though the Boss heads had to have their coolant passages slightly modified.
The 1969-70 302 H.O. engine was developed in 1968 for the SCCA's 1969 Trans-Am road racing series. Fitted to the factory-made Boss 302 Mustangs of 1969-70, it is a unique Ford small-block featuring a thin-wall casting. It differed substantially from regular 302s, featuring 4-bolt mains, screw-in freeze plugs, higher nickel content, and cylinder heads using a canted valve design developed for the 351C, which made its debut in late 1969 Mustangs.
The block had a thicker deck and a taller intake manifold due to the heads. It also had a distinct harmonic balancer, crankcase windage tray, bigger diameter alternator pulley (from the 289 HIPO), and bigger diameter power steering pulley all to accommodate the higher RPM capabilities of the engine vs a standard 302. While the standard 302 used six bolts on the valve cover, the Boss 302 has eight bolts. The valve cover was chromed in 1969 and changed in 1970 to cast aluminum. The connecting rods are the same as used in the 289 HIPO and have an engineering number of C3AE-D on them. They are capable of higher RPMs than standard 302 rods (up to ~8k RPM), aided by a spot face for 3⁄8 in (9.5 mm) bolts with a unique football-shaped head (vs 5/16 for standard small blocks), and beefier cap. The crankshaft is cross-drilled with hollow crankshaft throws (this was changed in 1970 for better reliability) high strength steel forging. The cam and lifters are high lift, solid mechanical units. The cam featured 290 degrees duration and .477 in (12.1 mm) of lift.
The wide and large port heads with staggered valve placement give the 302 H.O. high power capabilities. Because of the pent-roof design of the heads, the Boss also had forged pop-up pistons to achieve the desired 10.5:1 compression ratio. Early units were typically characterized by very large intake 2.23 inches (56.6 mm) and exhaust 1.7 inches (43.2 mm) valves sitting in a small quench style combustion chamber. Exhaust valves were sodium-filled to aid cooling. Valve springs were dual units with an inner and outer spring to minimize harmonic resonance at high RPM. The heads feature steel spring seats, screw-in rocker studs, pushrod guide plates to aid in pushrod stability at high RPMs, and adjustable rocker arms. Fuel was provided by a Holley 780 cu ft/min (22.1 m3/min) manual choke carburetor. The taller intake required a thinner spacer. Ford used a phenolic spacer that incorporated an aluminum tube for the PCV hose and also helped isolate the carburetor from the heat of the intake. Ignition was handled by a dual point distributor firing unique 14 mm (0.6 in) AF 32 Autolite spark plugs specified because of their smaller size (5⁄8-inch (15.9 mm) wrench vs. 13⁄16-inch (20.6 mm) wrench) so as to fit within the tight confines of the combustion chamber alongside the very large valves.
The motor produces a unique sound as a result of its solid-lifter configuration. At idle, properly tuned, the engine produced a significant amount of 'chatter' noise.
The power output was 290 hp (216 kW) at 5,200 RPM with maximum torque of 290 lb⋅ft (393 N⋅m) at 4300 RPM. It had a 6,250 RPM limit. The Boss 302 engine competes well with other high performance 'small blocks', such as the Chevy 302, the Chrysler 340, and the AMC 360.
The "Boss" in the Boss 302's name came from original designer Larry Shinoda's reference to Bunkie Knudsen, the CEO at Ford and an outspoken proponent of the car's development, who told his designers, "I want to design a car that's the coolest Mustang out there. I don't want somebody else's name on it, like a Shelby." Boss 302 is the name of the car (the engine is the 302 H.O.) but it also became popular to call this specific engine the Boss 302.
This engine was also optional in the Mercury Cougar Eliminator, with a total of 169 produced in 1969 and 469 assembled in 1970.
New Boss 302 (2007-)
The new Boss 302 engine was unveiled in the 2006 SEMA show.
In 2007, Ford Racing began marketing new crate engines using the "Boss 302" moniker with displacements between 302 to 360 cu in (4.95 to 5.9 L) that are rated from 340 to 360 hp (254 to 268 kW).
The double overhead cam, variable valve timing 444 hp (331 kW) Ford Modular "Coyote-Boss" engine is also marketed as a crate engine by Ford Racing.
- Holdener, Richard (2010-10-10). "Ford Boss 302 Engine Build - Build A Better Boss". Retrieved 2015-08-10.
- "Boss 302 Engine and Boss 302 Mustang History and Specifications". 302w.com. Archived from the original on 2010-11-21. Retrieved 2014-04-19.
- "Ford Racing brings the boss back with new line of BOSS 302 Crate Engines". Tuningnews.net. Retrieved 2010-07-15.