• An accurate torque wrench is critically important in correctly tightening the head bolts.torque wrench in box image by Christopher Dodge from Fotolia.com
  
  The 2.5 L 1991 Plymouth Acclaim is equipped with either a 2.5 L V6 engine with electronic fuel injection or a turbo-charged version of the same engine. The torque specifications are the same for both engines. The engine head holds in the cylinder pressure essential to combustion. Head bolts must be tightened precisely as specified by the engine manufacturer to ensure the engine cannot self-destruct.
  
  

Head Bolt Sequence

• The tightening sequence ensures even pressure across the headbolt image by martini from Fotolia.com
  
  Head bolts are each given a number to show the order in which they must be tightened. There are two rows of head bolts: the first row is closest to the firewall and the second closest to the front of the car. The head bolts in the first row are numbered from left to right 10, 6, 2, 3, 7 and the head bolts in the second row are numbered 9, 5, 3, 4, 8. You will tighten the bolts in sequence from 1 to 10. Follow the sequence and you will notice it makes a clockwise spiral pattern. This is done to ensure pressure on the head is spread evenly across the engine block.
  
  

Tightening Pattern

• Each bolt is tightened in four stages. Perform the first stage on bolt 1 then do the same on bolts 2 to 10. Then come back to bolt 1 and do the second stage of tightening to bolts 1 to 10, followed by the third and fourth stages.
  
  

Tightening Steps

• The first tightening step is to apply 45 foot-pounds of torque. Apply this to bolts 1 to 10 in order. The second step is to 65 foot-pounds. The third step is also to 65 foot-pounds. The fourth step is to tighten each bolt a further 90 degrees.