Bolt used for fastening crankshafts.
Bolts used for tightening timing belt pulleys-dampers and FEAD (Front Engine Accessory Drive) accessory components. May be individual bolts ranging from M12-M16, or multiple smaller bolts, usually 4-6 to M8-M10.
Must be able to guarantee a precise axial load since their purpose is to keep the pulley properly timed with the crankshaft on which the phonic wheel is also mounted. They have a 10.9, 12.9 strength rating with the possibility of being developed to higher specific ratings.
They work in the plastic range and are tightened based on torque plus rotation, they rarely have a thread lock and the individual bolts have large washers sometimes with specific shapes to ensure the best contact with the pulley.