Ford Boss 302 engine
| Ford 302 H.O. | |
|---|---|
 | |
| Overview | |
| Manufacturer | Ford Motor Company |
| Production | 1969-1970 |
| Layout | |
| 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) |
| Cylinder block material | Cast iron |
| Cylinder head material | Cast iron |
| Valvetrain | OHV 2 valves x cyl. |
| Compression ratio | 10.5:1 |
| Combustion | |
| Fuel system | Holley Carburetor |
| Fuel type | Gasoline |
| Oil system | Wet sump |
| Cooling system | Water-cooled |
| Output | |
| 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 |
| Chronology | |
| Successor | Ford Boss 351 V8 |
The Ford Boss 302 (formally the "302 H.O.") 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.[1] 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.[1]
An entirely new Boss 302 engine was introduced for the 2012 Ford Mustang using a variant of the Ford Modular engine.
Design[edit]
The 1969–70 302 H.O. engine was developed in 1968 for the SCCA's 1969 Trans-Am road racing series. Fitted to the contemporary factory-made Boss 302 Mustangs, the small block V8 differed substantially from stock Ford 302s, being based on a unique thin-wall, high nickel content casting, with performance upgrades that included solid lifters, much stronger 4-bolt rather than 2-bolt main crankshaft bearings, threaded rather than simple compression freeze plugs, and heads using a canted valve design that allowed for larger valves than on most engines more than a third greater in displacement.[2] These "better breathing" heads were being developed for the planned 351 Cleveland (which debuted in late 1969 Mustangs) and shared a common cylinder head bolt pattern, but required slight modification of their coolant passages to work on the Boss 302.[3]
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 a higher-revving engine than the standard 302. Valve covers gained two bolts (up to eight), and were chromed in 1969 and cast aluminum in 1970. 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 handling 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 was a cross-drilled high-strength steel forging with hollow crankshaft throws; the cross-drilling was eliminated in 1970 for better reliability. The cam and lifters are high lift, with the cam featuring 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.
At idle, a properly tuned engine's solid lifters produce a significant amount of 'chatter', giving the engine a unique sound.
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 6,150 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.[2]
The name "Boss", popular 1960s slang for "excellent" or "very cool",[4] got attached to the Boss 302 Mustang by stylist Larry Shinoda in recognition of the enthusiasm of his boss, new Ford president Semon "Bunkie" Knudson (who had brought Shinoda over from GM's Chevrolet Division)[5] for the car. Knudson 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."[citation needed] The model's widespread popularity resulted in the term "Boss 302" displacing "302 H.O.", the engine's formal name, in popular use.
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-)[edit]
The new Boss 302 engine was unveiled in the 2006 SEMA show.[6]
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.
Additional Information[edit]
The Boss 302 engine may be confused with the 302 Cleveland Ford small block engine, which was produced by Ford Australia. The 302 Cleveland is a (4.9L) engine that was exclusively made in Australia from 1971 to 1982 (see Ford 335 engine).
The Boss 302 and 302 Cleveland may also be commonly referred to as the 5.0 Liter or 302 5.0. This may have been to distinguish the engines from the 300 cu Ford straight-six engine, otherwise known as the 4.9L. Another possible reason for the 5.0 Liter title may be to separate the two similar engines from the 4.6 Liter series which came as a 302 as well as 289 and 351. [7]
Small Block and Cleveland, Boss difference[edit]
The Ford small block engine is the series of engines the Boss 302 was derived from. The original line of 302 engines was manufactured from 1969 to 1970. From 1968 to 1970, the engines were manufactured in Windsor, Ontario, and would be the base architecture of the Boss 302. In 1969, the manufacturing location of the Boss 302 changed to Cleveland, Ohio. After the location change, adjustments were made to the design of the Boss 302. The 1969 - 1970 Boss 302 engines shared the same heads as the Boss 351, (351C-4V canted valve). These heads were modified for the solid mechanical cams the Boss 302 and Boss 351 engine would come with. Adjustable rocker studs, new long slot rockers and closed 62cc combustion chamber heads were used.
The Boss engine, because it's a variant of the 302 small block. The difference between the canted valve Cleveland head 302 and the inline valve small block 302 is that the Cleveland used the base small block 302s short-block, and adds the unique Boss 302 heads to it. The Boss 302 block, designed for racing is 4-bolt main on the center three caps, made from high nodular iron, the same type as the 289 Hi-Po engine. The cylinder bores are notched slightly on the top to clear the big 2.19 Intake valves. This required a new head gasket for the Boss engines. The Rods are beefed-up versions of the 302. They are longer and share the same length as the 289 at 5.155 vs 5.09 for the 302W. The Boss engine used a steel crankshaft as well. And all Boss 302 and 351's came with a windage tray to skim oil away from the rotating parts for more horsepower. The canted Valve Boss engines use a piston specifically notched for the canted valve heads. Pistons are not interchangeable between a 302 small block and a Boss (Cleveland head) engine. The 351s heads allowed the Boss 302 to have a significant increase in airflow because of its canted or angled valves. In the canted valve heads the intake and exhaust valves are rotated so the intake valves are closer to the valley, providing a slightly better path of air in and out of the bores.[8]
See also[edit]
References[edit]
- ^ a b Holdener, Richard (2010-10-10). "Ford Boss 302 Engine Build - Build A Better Boss". Retrieved 2015-08-10.
- ^ a b "Boss 302 Engine and Boss 302 Mustang History and Specifications". 302w.com. Archived from the original on 21 November 2010. Retrieved 18 November 2010.
- ^ Erickson, Keith (17 July 2017). "Ford Boss 302 Engine Build – Build A Better Boss – Tech". Mustang and Fords.
- ^ "Boss" at Thesaurus.com
- ^ Hart, Roger (4 April 2011). "High-End Muscle". AutoWeek. 61 (7): 18.
- ^ "Ford Racing brings the boss back with new line of BOSS 302 Crate Engines". Tuningnews.net. Archived from the original on 2010-06-21. Retrieved 2010-07-15.
- ^ Shafer, Jason. "Engine History: The Ford 4.6 liter V8". Curbside Classis. Retrieved 13 February 2023.
- ^ Holdener, Richard. "Ford Boss 302 Engine Build - Build A Better Boss - Tech". MotorTrend. Retrieved 13 February 2023.