KDD Valve Springs 6.0/6.4 Powerstroke

Stock Plus (Stage 1/Standard) For a mild bump over used factory springs, we use these quality USA made valve springs as the standard spring for our popular o-ringed cylinder heads, perfect for the daily driver, tow rig, or mild performance upgrade looking for solid reliability. Used factory springs typically have around 60-70 psi at 1.865" installed height. These have 80 psi @ 1.865", we use these in all of our stock replacement cylinder heads.Street Performance Valve Sprigns (Stage 2) These street performance springs are ideal for trucks with moderate turbo and injector upgrades. We don't just offer a "one size fits all" valve spring, there's the right spring for the application, and "more isn't always better". These springs feature 100 psi at an installed height of 1.865". They're perfect for the street truck with a moderate sized single turbo (70mm+) capable of 50+ psi of boost, occasional track use (Large Compound Turbo and Nitrous applications should use the Stage 3 - Competition