Caterpillar C11, C13 Head Bolt Kit

Caterpillar C11, C13 Engine Head Bolt Kit 
Did you know? All Caterpillar C series engines require that the used head bolts be discarded and replaced with new head bolts every time there is a repair.
The way Torque-To-Yield bolts work is simple; the bolts are longer and thinner when compared to early bolt designs. When these bolts get torqued (tightened) to yield meaning to almost the breaking point, the bolts will stretch. This stretching (like a spring) provides a constant clamping force on the cylinder head.
Why you should never reuse TTY head bolts: Used TTY (Torque-To-Yield) head bolts will snap in the process of re-torqueing the cylinder head. If they do not snap, the already permanently stretched bolts will stretch even further and rapidly lose clamping load. The loss of clamping load could ultimately lead to head gasket failure.
When an engine operates, the cylinder head expands as it heats up and contracts when it cools down. The spring like clamping force of the TTY bolts allows for this expansion and contraction without losing the clamping pressure on the cylinder head, and thus maintaining the sealing integrity of the head gasket.
Kit Contains: (26) 2421811 - Head Bolts - M16 x 2 x 220, Hex Head, 12.9 Class (26) 2S5658 - Hardened Washers - 16.66 mm I.D. x 28.58 mm O.D. x 3.18 mm Thick - Hardened (8) 2104460 - Head Bolts - M10 x 1.5 x 130, Hex Head , 10.9 Class