2016-18. FRONT. Spring. A Spring Bolt, which is a specially designed shouldered Bolt with matching Spring and nut. It is designed to bottom out against the flange, which preserves the Spring's force (acting as a locking measure) without over-compressing it, which can lead to failures during the high temperature cycles found in Exhaust. These Bolts always mount through the flange, with a nut on the backside. A Spring that is placed between the Exhaust Bolt and flange and provides tension against the Bolt. A Spring which mounts between the Exhaust manifold Bolt and its mounting surface. Exhaust Manifold Bolt and Spring. Adjust plate. And. Bracket. Pipe. Pressure.