Diamond Power Intake & Exhaust Valves works with Jeep Grand Cherokee Comanche Wrangler 4.0L OHV 12V 2 Year Warranty (This product must be installed by a certified professional mechanic) Same day shipping when purchased before 3pm EST Our products are tested and meet or exceed OEM performance requirements Fits 87-92 Jeep Comanche 4-0L 3966CC 242CID OHV 12V L6 Engine Valves are made with excellent quality materials (Nickel, Chrome and Tungsten)