For the most part, there are three different types of fasteners used when building an engine. Some bolts, screws and studs can be reused and some should ALWAYS be replaced. The question is...what makes the bolts different? When building an engine, finding the specific torque and torque sequence based on the application is the first step in ensure all fasteners are tighten securely.
Torque Only Fasteners
Most time externally threaded bolts, screws and studs can be reused unless otherwise stated by the service manual or manufacturer. A conventional torque wrench should do the trick on
these types of bolts.
Torque with and Angle Fastener
Most fasteners that require and torque and angle tightening sequence can be re-used. The fastener is first torqued to a specified amount the and added angle tightening is added to secure the fastener. The angle sequence is an additional step that sometimes requires an additional wrench to prevent the fastener from rotating.
Torque-to-yeild fasteners are vary similar to the previously listed torque with angle fasteners, however they can not be re-used. Once a torque-to-yield fastener is tightened it becomes distorted. If they are ever loosened (even right after installation) they must ALWAYS be replaced.