What Is the Best Way to Torque Head Bolts Correctly?

Properly using an accurate torque wrench is the best way to torque head bolts correctly. Refer to the manufacturer for bolt torque and lubrication specifications Generally, cylinder head bolts require a light coating of 10W-30 motor oil, unless they are torque-to-yield bolts that are always inserted dry, to tighten properly.

Head bolts must be tightened in a specific sequence as well as to the correct torque. The pattern typically requires tightening bolts by alternating from side to side, or from the middle outward to equalize loading pressure on the castings and gasket. The allowable torque variance is generally plus or minus 3 percent.

Torque wrenches come in four types, with varying prices and accuracy associated with each. Either beam, or click adjustable, style torque wrenches can perform within the tolerance levels needed, and they are usually the least expensive. The beam style is the easiest to use and is relatively accurate as long as the bar is not bent. Click adjustable wrenches are also easy to use, but must be used by holding the grip or their accuracy is compromised. They also have an internal spring mechanism that may require calibration if subjected to heavy use.

Dial gauge and digital electronic models are more extremely accurate, but more difficult to use and very expensive. Their 0.5 percent tolerance significantly exceeds the requirements needed and is generally reserved for professional racing applications.