Type...........60 degree V12, pressure liquid cooled, 4 stroke, 48 valves,
supercharged, geared drive.
Construction...Two-piece Aluminium alloy crankcase, two-piece aluminium alloy
cylinder blocks, steel liners, 2 inlet valves and two sodium
cooled exhaust valves per cylinder, operated by single
overhead camshaft per bank. Forged steel crankshaft with marine
type fork and blade connecting rods, 7 main bearings, forged
aluminium alloy pistons. Spur reduction gear 0.42:1
Supercharger...10.2" dia Gear driven two speed, single (two) stage, ratios
8.15:1 and 9.49:1 (5.79:1 and 7.06:1)
Fuel System....SU AVT40 2 barrel updraught carburettor with automatic mixture
and boost control. (1 Rolls-Royce-SU SUX-601 variable stroke
fuel injection pump, discharging into eye of the supercharger
and automatic fuel/air ratio control)
Ignition.......Twin magneto: BTH C6SE12 or Rotax NSE12. 14mm x 14mm plugs
with screened cabling.
Lubrication....Dry sump, 60 psi main pressure feed
Starter........BTH CA4750, and provision for hand turning on wheelcase.
Bore...........5.4" 137mm
Stroke.........6" 152mm
Displacement...1649cu in 27 litres
Comp. Ratio....6:1
Width..........29.8" 757mm (30.7" 780mm)
Height.........43" 1092mm (39.9" 1014mm)
Length.........71" 1803mm (88.7" 2253mm)
Weight.........1540lb 698kg (1715lb 778kg)
Specific Output...1hp/cu in 60.7hp/litre (1.11hp/cu in 67.8 hp/litre)
Max piston speed..3000ft/min 15.2m/sec
Rating @ takeoff..1610hp/3000rpm/18lb boost (1645hp/3000rpm/18lb)
Rating-low gear...1635hp/3000rpm/2250ft (2020/3000/1500ft)
Rating-high gear..1510hp/3000rpm/9250ft (1845/3000/14250ft)
Rating-cruise.....1015hp/2650/15500ft (1190/2650/24250)
All engines ran on 100/130 grade Aviation Fuel, and a maximum consumption at take-off for the Merlin 24 was 150 gallons per
hour, or around 3 gallons per minute, dropping to half this when cruising typically.
Packard Merlin engines used a Bendix-Stromberg injection carburettor which did not have a float chamber, thus making it less
susceptible to cutting out during negative G manouveres, unlike the oil system!
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