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Ford Boss 302 engine
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{{Infobox automobile engine | image = Ford Boss 302 engine.jpg | name = Ford 302 H.O. | production = 1969-1970 | manufacturer = [[Ford Motor Company]] | configuration = [[Naturally aspirated]] 90° [[V8 engine|V8]] | bore = {{cvt|4|in|mm|1}} | stroke = {{cvt|3|in|mm|1}} | displacement = {{cvt|302|cuin|L|1}} | block = [[Cast iron]] | head = Cast iron | valvetrain = [[Overhead valve|OHV]] 2 valves x cyl. | fuelsystem = [[Holley Performance Products|Holley]] [[Carburetor]] | fueltype = Gasoline | oilsystem = [[Wet sump]] | coolingsystem = [[Radiator (engine cooling)|Water-cooled]] | power = {{cvt|290|hp|kW|0}} at 5200 [[Revolutions per minute|rpm]] | specpower = {{cvt|{{#expr:290/4.9 round 1}}|hp|kW|1}}/Liter | torque = {{cvt|290|lbft|Nm|0}} at 4300 rpm | compression = 10.5:1 | predecessor = | successor = [[Ford 335 engine#1971 R-code (Boss 351)|Ford Boss 351 V8]] }} The '''Ford Boss 302''' (formally the "'''302 H.O.'''") is a high-performance "small block" {{cvt|302|cuin|L|1}} [[V8 engine]] manufactured by [[Ford Motor Company]]. The original version of this engine was used in the 1969 and 1970 [[Boss 302 Mustang]]s and Cougar Eliminators and was constructed by attaching heads designed for the planned [[Ford 335 engine#351 Cleveland|351 Cleveland]] (which debuted the following year) to a Ford small block.<ref name="maf-oct2010"/> 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.<ref name="maf-oct2010"/> An entirely new [[Ford Modular engine#Boss 302 .28Road Runner.29 Variant|Boss 302 engine]] was introduced for the 2012 Ford Mustang using a variant of the [[Ford Modular engine]]. ==Design== The [[Ford small block engine|Ford small-block V8]]-based 1969–70 302 H.O. "[[Ford small block engine#Boss 302|Boss 302]]" engine was developed in 1968 for the [[Sports Car Club of America|SCCA]]'s 1969 [[Trans-Am Series|Trans-Am]] road racing series. Available only in the [[Boss 302 Mustang]], it derived from a line that traced to the [[Ford small block engine#289 HiPo (K-code)|Ford 289 HiPo]] engine, not a stock "Windsor" 302. It had its own block, based on a unique thin-wall, high nickel content nodular iron casting, with performance upgrades that included [[valve lifter|solid lifters]], much stronger 4-bolt rather than 2-bolt main [[crankshaft]] bearings,<ref name=hc>[https://heacockclassic.com/articles/fords-boss-302-boss-429-mustangs/ Ford’s Boss 302 & Boss 429 Mustangs], Heacock Classics</ref> threaded rather than compression freeze plugs, and custom-fitted canted valve [[cylinder head|heads]] that gave it larger valves than on most engines more than a third greater in displacement.<ref name="302w">{{cite web|url=http://www.302w.com/boss-302/boss-302-engine-history-and-technical-specifcations.aspx|title=Boss 302 Engine and Boss 302 Mustang History and Specifications|publisher=302w.com|access-date=18 November 2010|archive-url=https://web.archive.org/web/20101121060802/http://www.302w.com/boss-302/boss-302-engine-history-and-technical-specifcations.aspx|archive-date=21 November 2010|url-status=dead}}</ref> These "better breathing" heads<ref name="maf-oct2010"/> were being developed for the planned [[Ford 335 engine#351 Cleveland|351 Cleveland]] (which debuted in late 1969 Mustangs) and shared a common [[cylinder head]] bolt pattern, but required slight modification of their coolant passages and special head gaskets to work on the Boss 302.<ref name="maf-oct2010"/> Adjustable rocker studs, new long slot rockers, and closed 62cc combustion chamber heads were all used. The block had a thicker deck and a taller [[intake manifold]] to accommodate the heads. The engine 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 high-performance [[connecting rod]]s are the same as used in the 289 HiPo, 5.155" vs 5.09" for the stock Windsor 302. They are capable of handling up to approximately 8000 rpm, aided by a spot face for {{cvt|3/8|in|mm|1}} 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 {{cvt|.477|in|mm|1}} of lift. The wide and large port heads with staggered valve placement give the 302 H.O. high power capabilities.<ref name=hc/> 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 {{convert|2.23|in|mm|1}} and exhaust {{convert|1.7|in|mm|1}} valves sitting in a small quench style [[combustion chamber]]. [[Exhaust valve]]s 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 arm]]s. Fuel was provided by a [[Holley Performance Products|Holley]] {{cvt|780|cuft/min|1}} manual [[Choke valve|choke]] carburetor. The taller intake required a thinner spacer, which incorporated an aluminum tube for the PCV hose and was made of phenolic resin to help isolate the carburetor from the heat of the intake. Ignition was handled by a dual point [[distributor]] firing unique small-diameter {{cvt|14|mm|in|1}} AF 32 [[Autolite]] [[spark plug]]s necessary to fit within the tight confines of the combustion chamber alongside the very large valves. [[File:Boss302Engine.jpg|alt=Ford Boss 302 Engine With Shaker scoop. Factory Finned Aluminum valve covers unique to canted valve Boss 302 engine. |thumb|285x285px|Ford Boss 302 Engine With Shaker scoop. Factory Finned Aluminum valve covers were unique to the canted valve Boss 302 engine.]] At idle, a properly tuned engine's solid lifters produce a significant amount of 'chatter', giving the engine a unique sound. Redline was 6,150 rpm, and power output conservatively rated at {{cvt|290|hp|kW|0}} gross at 5,200 rpm with maximum [[torque]] of {{cvt|290|lbft|Nm|0}} at 4300 rpm. The Boss 302 engine competes well with other high performance 'small blocks', such as the [[Chevrolet small-block engine (first- and second-generation)#302|Chevy 302]], the [[Chrysler LA engine#340 V8|Chrysler 340]], and the [[AMC V8 engine|AMC 360]].<ref name="302w"/> The name "Boss", popular 1960s slang for "excellent" or "very cool",<ref>[https://www.thesaurus.com/browse/boss "Boss" at Thesaurus.com]</ref> got attached to the Boss 302 Mustang by stylist [[Larry Shinoda]] in recognition of the enthusiasm of his boss, new Ford president [[Bunkie Knudsen|Semon "Bunkie" Knudson]] (who had brought Shinoda over from GM's Chevrolet Division)<ref>{{cite journal|last=Hart|first=Roger|title=High-End Muscle|journal=AutoWeek|date=4 April 2011|volume=61|issue=7|page=18 }}</ref> 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|date=November 2016}} 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#First generation (1967–1970)|Mercury Cougar Eliminator]], with a total of 169 produced in 1969 and 469 assembled in 1970. ==New Boss 302 (2007-)== {{main|Ford Modular engine#Boss 302}} The new Boss 302 engine was unveiled in the 2006 SEMA show.<ref>{{cite web |url=http://www.tuningnews.net/article/061031c/ford-racing-mustang-boss-302/ |title=Ford Racing brings the boss back with new line of BOSS 302 Crate Engines |website=Tuningnews.net |date= |accessdate=2010-07-15 |archive-date=2010-06-21 |archive-url=https://web.archive.org/web/20100621043539/http://www.tuningnews.net/article/061031c/ford-racing-mustang-boss-302/ |url-status=dead }}</ref> In 2007, [[Ford Racing]] began marketing new crate engines using the "Boss 302" moniker with displacements between {{cvt|4.95 to 5.9|L|cuin|0|disp=flip}} that are rated from {{cvt|340 to 360|hp|kW|0}}. The double overhead cam, variable valve timing {{cvt|444|hp|kW|0}} [[Ford Modular engine#5.0.C2.A0L Coyote|Ford Modular "Coyote-Boss" engine]] is also marketed as a crate engine by Ford Racing. ==See also== *[[List of Ford engines]] ==References== {{reflist|refs= <ref name="maf-oct2010">{{cite web |url=http://www.mustangandfords.com/how-to/engine/mdmp-1011-ford-boss-302-engine-build/ |last=Holdener |first=Richard |website=www.mustangandfords.com |title=Ford Boss 302 Engine Build - Build A Better Boss - Tech |date=2010-10-21 |publisher= |access-date= |archive-url=https://web.archive.org/web/20190718183338/http://www.mustangandfords.com/how-to/engine/mdmp-1011-ford-boss-302-engine-build/ |archive-date=2019-07-18 }}</ref> }} ==External links== *[http://www.fordracingparts.com/download/instructionsheets/FordInstShtM-6010-BOSS302.pdf BOSS 302 Cylinder Block instruction sheet] *[https://web.archive.org/web/20111009165434/http://www.livedash.com/transcript/mustang_boss_302/4080/SPEED/Wednesday_January_5_2011/543883/ Boss 302 "Ford Remakes a Legend"] *[https://heacockclassic.com/articles/fords-boss-302-boss-429-mustangs/ "Ford’s Boss 302 & Boss 429 Mustangs", Heacock Classics] {{DEFAULTSORT:Ford Boss 302 Engine}} [[Category:Ford engines|Boss 302]] [[Category:V8 engines]] [[Category:Gasoline engines by model]]
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