These Drop-in springs are an upgraded direct replacement for the stock 2.3 valve springs used in turbo and N/A engines. The stock springs are 75lb pressure brand new while these bump up pressure to 105lb seat pressure making them a great upgrade for slider cams and small hydraulic roller cams like our stage 1 cams.  They can also be shimmed .060" to bump seat pressure up to 117lb closed ideal for mechanical flat tappet or high rpm (6000+) hydraulic roller. They are designed to sit directly on a stock heads spring seats without the factory spring buckets. They work with stock valves, retainers and locks. Price is for set of 8 springs.