• Ford produced the Mustang with only two engine options for the 1991 model year, the 2.3-liter four-cylinder engine and the 5.0-liter eight-cylinder engine. The 2.3-liter was standard equipment, and the 5.0-liter was optional equipment as part of the GT package. However, the 5.0-liter engine was the only available engine for the Cobra version of the Mustang. Generally, each engine has its own torque specifications that must be carefully followed upon reassembly.
  
  

Cylinder Head

• The cylinder head fasteners must be tightened in two intervals for both engines. If working on the 2.3-liter engine, torque each fastener to an initial setting of between 51 and 59 ft.-lb. of torque, then tighten each fastener to between 80 and 90 ft.-lb. of torque. If working on the 5.0-liter engine, tighten each fastener to an initial setting of between 18 and 24 ft.-lb. of torque, then tighten each fastener to between 65 and 72 ft.-lb. of torque.
  
  

Main Bearing Caps

• Tighten each main bearing cap fastener to between 80 and 90 ft.-lb. of torque if working on the 2.3-liter engine, and to between 60 and 70 ft.-lb. of torque if working on the 5.0-liter engine.
  
  

Rod Bearing Caps

• The rod bearing cap fasteners must be tightened in two intervals for the 2.3-liter engine. First, torque each fastener to an initial setting of between 25 and 30 ft.-lb. of torque, then tighten each fastener to between 30 and 36 ft.-lb. of torque. If working on the 5.0-liter engine, tighten each fastener to between 19 and 24 ft.-lb. of torque.
  
  

Exhaust Manifold

• The exhaust manifold fasteners must be tightened in two intervals for the 2.3-liter engine. First, torque each exhaust manifold fastener to an initial setting of between 178 and 204 in.-lb. of torque, then tighten each fastener to between 20 and 30 ft.-lb. of torque. If working on the 5.0-liter engine, tighten each fastener to between 18 and 24 ft.-lb. of torque.
  
  

Intake Manifold

• Tighten the intake manifold fasteners to between 19 and 28 ft.-lb. of torque if working on the 2.3-liter engine. The intake manifold fasteners must be tightened in two intervals for the 5.0-liter engine. First, torque each intake manifold fastener to an initial setting of between 15 and 20 ft.-lb. of torque, then tighten each fastener to between 23 and 25 ft.-lb. of torque.
  
  

Rocker Arm Cover

• Tighten each rocker arm fastener to between 62 and 97 in.-lb. of torque for both engines.
  
  

Oil Pan

• Tighten each oil pan fastener to between 71 and 106 in.-lb. of torque for both engines.
  
  

Oil Pump

• Tighten each oil pump fastener to between 14 and 21 ft.-lb. of torque if working on the 2.3-liter engine, and to between 22 and 32 ft.-lb. of torque if working on the 5.0-liter engine.
  
  

Thermostat Housing

• Tighten each thermostat housing fastener to between 14 and 21 ft.-lb. of torque if working on the 2.3-liter engine, and to between 12 and 17 ft.-lb. of torque if working on the 5.0-liter engine.
  
  

Vibration Damper

• Tighten the vibration damper's retaining bolt to between 70 and 90 ft.-lb. of torque for both engines.