A factory head bolt design, even TTY (torque-to-yield) hardware, provides adequate strength at stock performance levels. However, these bolts become undesirable and significantly more likely to fail as performance levels are increased. The actual realized power level that the factory hardware will fail varies considerably from engine to engine. Some engines, namely the 6.0L Power Stroke, are more sensitive to power increases than others. In general, the greater the performance increase, the greater the likelihood that a failure will occur. Fortunately, replacing the factory head bolts with stronger head studs significantly reduces the chances of a failure and "studded" engines can reach significant performance levels with limited concerns with regard to cylinder head lifting and head gasket failures.
The strength of a head bolt is characterized by the cross sectional area and the material properties of the bolt. Additionally, OE designs typically employ the use of TTY hardware, which can only be torqued once - after an initial torque sequence is applied to the bolts, they are to be discarded if and when they are removed. This is where upgraded head studs come into play, featuring significantly more desirable material properties. Not only do they exhibit greater resilience to stress, but they stretch much less under load, thereby reducing the likelihood of a head gasket failure resulting from cylinder head lifting.
Head studs are a relatively expensive upgrade, but highly recommended in performance builds. Most engines will survive the performance levels achieved by aggressive tuning ("race tunes") and basic bolt on modifications, however, there is no denying that a fatigue failure is much more likely in these instances. For engines that have received extensive fuel system modifications, upgrading to head studs may be considered mandatory. Large injectors, injection pump upgrades, and any other modification that increases fuel and airflow significantly should be accompanied by the installation of head studs and performance head gaskets.
Fire Ringed Cylinder Heads
For more intense engine builds, the cylinder head gaskets can be superseded with the installation of fire rings. In a fire ringed cylinder head, a small groove is machined into the cylinder head around each individual combustion chamber. A metal ring is then inserted in this groove, which positively seals to the engine block once the cylinder head is torqued down. Therefore, in a fire ringed cylinder head the head gasket no longer must resist the pressure created in the cylinder and only needs to seal water and oil channels between the cylinder head and engine block. This provides a greater seal around the combustion chamber and, with the addition of head studs, is the highest strength option available.
Fire ringing is tedious and relatively expensive since the work must be carried out by a machine shop with specialized equipment. However, it is very common in high performance builds and is the upgrade of choice for serious race and pulling trucks. For most street-able pickups, fire ringing is overkill and the installation of head studs and quality head gaskets should provide more than enough peace of mind.