× 90 mm 239 bhp (180 kW)@6750rpm. for F1 1961 FPF 2751 cc 4 cyl 96 mm × 95 mm Indianapolis and Formula Libre 1961 FPF Mk.II 1499.8 cc 4 cyl 82 mm × 71 mm 151 bhp (113 kW)@7500rpm for F1 See the below F1 engines section for comparison to other models. FWM The FW was designed in response to the British Government's Defence Ministry (MoD) requisition outline issued in 1950, specifying a water pump and petrol engine combination to deliver 350 gallons of water per minute at 100 psi, with 35 to 40 bhp at the weight of 350 pounds or less. The successful bid by a portable pump driven by the 38 bhp FW mounted in a steel pipe frame resulted in a 5000 unit supply contract in 1952. By 1956, 1460 cc FWB was adapted back to a higher output fire pump engine as FWBP with good results, and led to the realisation that the newer 35 hp general purpose engine specification by the government (including for Search Lights and Generator Sets) could be met with a smaller displacement engine. This resulted in the development of SOHC 654 cc (2.35" bore x 2.25" stroke) FWM in 1957, which basically was a smaller and lighter version of FWP with many detailed differences that reflect the improvements and cost-cutting as well as weight-saving measures found in the development of FWA, FWB, and FWE. The differences include: Deletion of the intermediary shaft (Jackshaft) making the cam drive a single stage chain as opposed to FW series' two stage gear/chain set up. This made the camshaft turn in the same direction as the crank. Conrod big end part line was made horizontal, as opposed to the previous diagonal. The number of cylinder head studs was reduced from 18 to 10. Evolution FWM was then developed into an automotive engine as FWMA of 742 cc with larger 2.45" bore and 2.4" stroke in 1959. Several versions of FWMD diesel utility engines, including a marine version, followed, and then a chain-driven DOHC 2 valves per cylinder crossflow cylinder head was developed and became the FWMC, succeeding FWC as the all-out racing engine for the 750cc class. FWMC became known for the unusually loud and high-pitched exhaust note when installed in a specially made super-light version of Lotus Elite run by UDT Laystall at 1961 Le Mans 24 Hours. It was this 4