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Title Shelby cars north west, factory authorized dealer for shelby automobiles


Roush Engine 427IR

427IR - This engine gets 50 more horsepower and an additional 35 lb.-ft. of torque than the 402IR, but has the same combination of a “Weber Style” 8-Stack Fuel Injection Induction System utilizing Roush Engineered calibration.

Technical Specs

Engine Model: 427IR 8-Stack Fuel Injection
Horsepower (maximum):
560 hp (8 qt. Oil Pan)
Torque (maximum): 540 ft. -lbs.
Displacement: 427 cu. in.
Block: 9.5” deck, Dart 4-bolt main
Crankshaft Type:
Forged 4340 Steel (Internally Balanced)
Bore and Stroke: 4.125” x 4.00”
Connecting Rod Type:
Forged 4340 Steel “H-beam”
Compression Ratio: 10.25:1
Wiseco Forged w/ Plasma Moly Rings & Lightweight Pins
Timing Chain: Double Roller
Camshaft Info: Roush Proprietary
Lifter Type: Hydraulic Roller
Cylinder Heads: Aluminum
Intake Runner Volume:
205 cc, fully CNC ported
Combustion Chamber Volume: 61 cc
Valve Sizes: 2.08” Intake 1.600” Exhaust
Rocker Arm Ratio:
1.6:1/Full Roller, Extruded Aluminum Body
Spark Plugs:
Autolite 3923 (or comparable)
Intake Manifold:
“Weber Style” 8-Stack Induction System

Fuel System:
Electronic Fuel Injection utilizing Roush Calibration Dual Sync. Distributor, Electric “High Volume” Fuel Pump, Wide Band 02 Sensor, Intake Temp. Sensor, Engine Coolant Sensor, MAP Sensor, IAC (Idle Air Control), and Ignition Control Box.
Fuel Requirements:
Premium Unleaded (minimum)
Max. Recommended RPM: 6,250
Firing Order: 1-3-7-2-6-5-4-8
31 to 34 degrees @ 4,000 rpm (not to exceed 35)
Oil Pump: High Volume - Adjustable
Oil Pan:
Powder Coated 8 qt. Front Sump - Baffled or Dual-sump (Mustang) available *horsepower output can be reduced when engine is equipped with the Dual-sump pan
Oil Filter:
Motorcraft FL-1HP (or comparable)
Oil Weight:
10w30 - non synthetic for first 3,000 miles
SFI Rated Steel, 157 Tooth Ring Gear
Powermaster High Torque Gear Reduction (or equivalent)

Roush 427IR Dyno