Tomei Timing Belt GuideTomei Timing Belt Guide. The timing belt guide provides your engine with extra insurance in the unfortunate event of one of the pulleys coming loose which can cause your belt to lose tension which can cause your pistons to make contact with the valves. More importantly, the Tomei unit is a direct replacement for the weaker design of the OEM unit. Features: Straight cut from aluminum Designed with an extended length to securely apply more tension to