High rotating weight is comparatively harmless (although is does reduce low gear acceleration).
Reciprocating weight is what breaks rods (and pulls pins out of piston), especially closing the throttle @ high RPM in the traps in which 14.7 lbs. per square inch of vacuum is added to the piston weight. With a 4.25" piston, that's 208 lbs. each...
The tension load on the rods varies directly as the reciprocating weight, but as the square of the RPM: 8,000 is not 14.3% greater than 7,000 (8 ÷ 7) but 30.6% greater (8^2 ÷ 7^2).
W/r/t "they do it all the time": where is the spark set?
