DescriptionDieselTuff  XHD 12v Conical Springs, Locks & Retainer kitFor the 1989-98 12v 5.9L engines. Spring Specs:175 lb seat pressure at installed height…well within safe for everyday use and moderate competitionCoil binds 1.220Designed for up-to 5,000rpmsafe for daily driving & competition capable conical spring design made in the USA with 10 deg chrome molly steel locks & retainersIf you’re running over 40psi & 3700rpm, this is one of the kits for you.HD Pushrods are required to run this kit…sold separately If you are running higher boost then stock, these springs will help the valves from being pushed open and bounce which can cause damage &/or cost you 10-12hp and efficiency. High Boost capability This conical valve spring system has been engineered to work in unicen with all of its included components to provide the best overall valve train stability. Our kit will include 12 valve springs, (12) chrome molly steel retainers and (24) valve locks to give you everything you need to upgrade the cylinder heads valve spring assembly.Designed with the capability to be used in applications from stock rebuilds, to all out built trucks.With higher boost capability, conical spring shape and increased rpm capability which allows for maximum spring stability at high rpm, while also having a much lower amount of stress that the spring wire will have to live with. This in turn increases service life even in low rpm applications, while having a 5,000 rpm capability.Increased valve spring seat pressure to 175 lbs to retain control of the valves to a higher PSI of boost, but will remain safe to run with the factory flat tappets.Chrome molly retainers that have been designed to mate perfectly with the beehive spring shape. This retainer saves weight and much stronger than OEM and other aftermarket retainers because of its reduction in size & design.Also included are 10 deg valve locks to pair with these new retainers. Don’t be fooled by people selling cheap springs out there. A broken spring can take out an engine.