The engine builder often focuses on the selection of appropriate components for an engine build. They also determine proper clearances, intake, exhaust volume, and flow. Threaded fasteners are the critical link that holds everything together. This is often assumed. This article will discuss various issues and concerns that directly relate to the most crucial components of any engine: studs, bolts, and their handling.
Studs
When possible, Barra head studs should be used for performance and heavy-duty applications. Because the studs do not twist when tightened, you can get more accurate torque values. The Barra head studs can be tightened by only one axis, so the clamping force is more accurate and even. This is especially true when dealing with alloy blocks. Studs can also be used to make main caps easier to install and aid in alignment. The Barra head studs can be clamped in a stationary position, which reduces the chance of the main cap falling off.
Installation tips
Before you start installing, make sure to thoroughly clean the blocks, caps, and studs. Any debris that is on the threads may affect thread engagement and lead to incorrect torque wrench readings.
You should chase the threaded holes on the female side of your block to make sure they are straight and even. Do not use cutting tape to accomplish this task. This will cut, shave or remove thread material and can decrease thread strength. You should use dedicated thread chasing tools, which will “form” the threads instead of cutting them. Your torque wrench must be calibrated. At least once per year, all torque wrenches need to be calibrated. If they are used frequently, this should be done more often. New torque wrenches also need to be checked for calibration. It is not unusual for some wrenches, even new ones, to be out-of-spec by up 10 ft.
You should use consistent tightening techniques. Don’t be quick to turn nuts on one side and slow on the other. It is best to gradually “creep” towards the pre-set value. Uneven and inaccurate values can be achieved by quick-bagging to reach the “click”, on a click-type, ratcheting torque wrench.
The majority of the time, screw the studs into a block finger tightly only. However, some manufacturers recommend a slight pre-load of 8-10 ft. A pre-load of approximately 8 to 10 ft. Double-nut the stud, and do not tighten too much. Remember that the torque value you are given for the installation is only for tightening the nuts, and not the stud.
You can have the studs chemically attached to block threads if you prefer a “fixed” install (which locks the studs in their place for future servicing). Heat can be used to break down the compound if the need arises to remove the studs. Use a locking agent to prevent stud misalignment. Install the cap before the thread compound hardens by tightening the nuts. This allows the thread compound to harden before it is placed on the required preload.
You don’t need to use a locking compound unless you want to keep the studs in place during quick main cap changes.
Simply ensure that all threads are engaged when installing the studs. Simply put, ensure the studs are installed “bottom-out”, with all threads engaged.
Install the studs and the main caps once they are in place. Check for alignment between studs and caps.
The block must be aligned honed if it is to achieve the best long-term results. Also, do not use bolts if you switch to studs. You should use the same fasteners for the main caps that you will use during the final assembly.
Cylinder head studs
Similar to main studs but with bolts, studs are preferred over bolts. This can vary depending on the application. For street engine applications, where it is difficult or impossible to remove the heads while the engine is still in place, studs might not be the best choice for cylinder head servicing. Bolts might be better if a master cylinder or other component makes it impossible to remove or install ahead of a cylinder with the engine in place. The use of studs, however, will theoretically make a better assembly if circumstances allow.
Head studs are a great way to help with cylinder head installation. This is especially useful for applications that require frequent head removal.
The use of bolts offers a more precise and consistent torque loading in terms of their function. Bolts are subject to both twisting and stretching when tightened. This causes the bolt to be exposed simultaneously to two forces and frictional loads at its thread engagement. When the nut on a bolt is tightened, it stretches only on its vertical axis. The exposed end (top of) the stud has “fine” threads. These threads allow for precise and accurate torque readings when torqued or torque/angle tightened to spec.