In the early 2000's I worked as a race mechanic and pit crew member for an ARCA Series team, which uses old NASCAR Cup cars and engines, but is run on a fraction of the budget. The better off teams could runs the engines at their NASCAR design RPM of roughly 9000-9200 RPM for that era. (Eventually, the engines were knocking on 10,000 RPM before NASCAR mandated spec rear end gear ratios to save development costs). The team I worked for was decidedly low budget, and we would gear the car to turn the engine much slower to avoid wear and tear on the parts. It worked well, but the change of running those engines at 8000-8200 RPM instead of the higher number was brutally hard on valve springs, especially at tracks like Pocono and Michigan with very long straightaways. It wasn't uncommon after a 200 mile Pocono race to have 2-4 broken valve springs. The springs had an inner and outer spring, and would usually only break outer one, so the engine would only lose power, not drop the valve onto the piston.
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