This Double Progressive Springs are an improvement over the regular valve spring. Developed with well known Tuners and Raceteams. The initial seat pressure was raised slightly to minimise valve float. Good for 7.500 rpm. A sound replacement for older engines during routine rebuild. Motorsport valve Spring increases the security reserves for overwinding the engine dramatically. Standard valve springs have approximately a spring rate of 85 kg before they reach full block. Motorsport valve springs have up to 105 kg. The desired value in Motorsport is 100 kg. minimum. Under 100 kg. the velves do not close properly at the higher rpm range and results in a dramatic loss in power.