Converter spring. W/O TURBOCHARGER. 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. Muffler AND. Included with: Converter and Pipe.