These engines are more relaible than most people think, although some are more maintenance intensive than others, particularly the valve springs (due to the weight of the OEM Style valves/springs/retainers, ramp speeds of the cam lobes and RPM). Anybody "pushing the envelope" is going to experience some damage in the short term in the constant search of a quicker ET. As an example, we used to get over 200 passes from a set of valve springs w +.950 lift and 8000 rpm shifts, that number fell to 85 passes at 8600 rpm shifts, less than 40 passes at 9000, even less at higher speeds. Reducing rotating weight within the rules is a challenge, and strength of parts vs weight and RPM is another. Increasing mass airflow through the engine is a huge challenge, given that you are restricted to an intake port volume of 189cc, and OEM style and size of carbs.