Why must the cylinder head bolts be tightened using multiple phases?

On applications with more than one fastener, such as wheel nuts or cylinder head bolts, the fasteners should be tightened to specification by alternating between the fasteners to ensure the parts are not distorted and that the fasteners are torqued evenly.

Why is uniform tightening of cylinder head bolts important?

The bolt tightening force is an important factor for the mutual sealing of combustion chamber, lubricant and coolant channels, and the ambient air. When tightening (torquing) the cylinder-head bolts, the bolt force generates the so-called surface pressure, which is essential for achieving a perfect seal.

Why are the head bolts torque in a certain pattern?

In the instruction manual, a torque sequence is specified. The overall goal is to spread the torque evenly as you are tightening the bolts. Usually, you start at one bolt, and you work your way around in a circular pattern. Doing so ensures that your head won’t be warped during the tightening sequence.

Why are cylinder head bolts loosened and tightened in a specified sequence?

Tightening a bolt stretches it, while pulling the head and block together. These bolts elastically deform and return to their original dimensions when loosened. Friction between the bolt head, its washer, and the cylinder head isn’t consistent.

Why should cylinder base nuts be tightened evenly and in correct sequence on engine cylinders?

This pattern helps to evenly apply the clamping force along the surfaces where the cylinder head meets the engine block. If this pattern is not followed or the bolts not tightened evenly, the result can be weak spots where cylinder pressure can escape, or warping of the cylinder head surfaces.

What is torque sequence?

Bolt tightening sequence, or torque sequence, is defined in the torque tightening procedure. Flange joints are torqued tight with the help of a torque wrench (manual or hydraulic). Torque bolts and nuts in a “CRISS-CROSS” sequence using a minimum of three torquing passes and the maximum bolt stress as defined.

What is the cylinder head bolt torque?

Tighten each bolt to 12-15 foot pounds of torque. 3, Tighten each bolt to 22-25 foot pounds of torque.

What is the correct sequence of loosening the cylinder head bolt?

Initially tighten all the bolts, in the sequence specified in the shop manual, to 30 to 44 foot-pounds. Next, loosen them in the same sequence by one-half a turn. Again tighten them, in sequence, to 30 to 44 foot-pounds. Next, turn all the bolts, again in sequence, by 90 degrees.

What is a torque sequence?

What is the torque setting for cylinder head bolts?

With the engine cold, tighten the cylinder head bolts, in sequence in 2–3 steps. Final torque on bolts 1–10 should be 65–72 ft. lbs. (88–98 Nm) and on bolts 11 and 12, 11–16 ft.

What are cylinder head bolts?

Cylinder-head bolts are the connecting elements between engine block, cylinder-head gasket, and cylinder head. The bolt tightening force is an important factor for the mutual sealing of combustion chamber, lubricant and coolant channels, and the ambient air.

What does a typical cylinder head tightening sequence look like?

For example, a typical cylinder head tightening sequence might look like this- Tighten all bolts in sequence, and in two stages to a snug torque value of say, 30 Nm Apply a 90 degree rotation to all bolts in the proper tightening sequence Apply a further 90 degree rotation to all bolts in the proper tightening sequence

What happens when a torque to yield cylinder head bolt is tightened?

When a torque to yield cylinder head bolt, or for that matter, any other critical torque to yield engine bolt is tightened, it undergoes two important phases, these (for our purposes) being the- In this phase, the bolt is stretched as torque is applied to it, but should the torque be removed the bolt will return to its original length.

How do you tighten a 3114 cylinder head?

Install and tighten the bolts as follows: 3114 Cylinder Head Tightening Sequence 3116 & 3126 Cylinder Head Tightening Sequence a. Tighten large bolts (1) in the number sequence s hown to a torque of 150 ± 15 N m (110 ± 11 lb ft).

What happens when you tighten the head gasket on a cylinder?

The same is happening with the head gasket during tightening the head screws (which are also quite special parts). Tightening in the correct order flattens the gasket properly. Any remaining bumps or voids result in tensions and weak points which might contribute to deformation and failure of the cylinder head or gasket leaks.