The Ford 302 H.O. is a high-performance "small block" 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. An entirely new Boss 302 engine was introduced for the 2012 Ford Mustang using a variant of the Ford Modular engine. Design 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, it is a unique Ford small-block featuring a thin-wall casting. It differed substantially from regular 302s, featuring four-bolt main bearings, 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 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 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