Melling Timing Chain Tensioner (MEBT5174)LS TIMING CHAIN TENSIONER Suit GM LS Series Part Number: MEBT5174 Timing chains stretch over time and become slack. Mellingtiming chain tensioners will retain the efficiency of your timing chain. These quality built steel componentskeep your chain under the proper tension for optimum performance in your engine. So, if your old tensioner is allowing your timing chain to "slack off," replaceit with a Melling!