[Henry Schmidt]

The springs we use are Aasco. Randy had them designed back in the early IMSA days to provide the seat and over the nose pressures required for the 8000+ rpm 2.5 GTU engines.
We've used them successfully for 35 years with zero failures from breakage and good results post over-rev. I believe part of the success lives in the lowest over-the-nose pressure possible for high lift applications. Most of the after markets [racing] springs we've tested have stupid high pressures. Silly numbers like 400+lb @ .500" lift. Things change, engineering and materials evolve over time but to date, we've have never seen a better spring for two valve 911 engines. .