I built my engine "all at once" so it wasn't possible to discern what effect the rockers by themselves had. However, when you stop to think that fully compressing just ONE valve spring can require 300+ pounds of force it's not hard to understand why operating the valve train is one of the largest causes of parasitic power loss in an engine. Still, there are compromises. Contrary to popular belief the Pontiac factory engineers weren't idiots. Those stamped steel rocker ball setups they designed (which, by the way are THE reason the small block chevy ever came to exist) are very strong, durable, and reliable. When you replace them with "something else" you've got to pay more attention to them in keeping on the lookout for wear and damage that can lead to failure and a destroyed engine. It just comes with the territory.