Tired of trying to consistently set your timing belt tension to a suitable level for your high-performance D-Series engine? Those days are over thanks to our solution to this common problem. The SpeedFactory Racing D-Series HD Timing Belt Tensioner Spring is made from durable & corrosion resistant 302 stainless steel and is over 6x stronger (the OEM spring is very weak & we found the need for a much higher spring rate). This high-quality spring gives your timing belt the proper tension level for high-performance and racing applications, especially when using a heavy-duty racing timing belt (such as Gates Racing) which are much stiffer & stronger than an OEM type belt. Not enough tension (OEM spring) and you get excessive belt deflection with poor cam timing control and a high risk of jumping teeth resulting in expensive valve damage or worse. Pulling on the tensioner with a hook to try and get enough tension has been a work-around but yields non-repeatable results at best and easily results in over-tightening which can cause undue stress on the belt and cam journal wear issues. This is what we use for our own top level engine builds with no other form of additional tensioners. No timing belt skipping, no cam journal wear issues, just reliable and consistent belt tension that works!