Dual valve spring kit

For the most extreme Miata engine. If you're building a track car and are planning on extended run time above 7500 rpm or boost 18 psi or more - they're what you need. Aluminum spring seat, chrome silicon steel springs, and titanium retainer. Sold in sets of 16 for a complete head. Fits all BP (1.8L) engines in both NA and NB Miatas. NA valves will require the use of valve keepers from an NB engine (not included). Seat pressure: 85 lb @ 33.60 mm Open pressure: 205 lb @ 10 mm Max lift: 12.90 mm Coil bind: 20.70 mm