Originally posted by drift
true to a point, but the rod/stroke ratio says you're incorrect about 8500rpm. the cranks are balanced to 10k rpm by Honda... but no one said the bearings will withstand all the lateral forces from rotation. constantly ramming into redline will reduce the life of the motor significantly as the motor is not designed to be revved that high. anyways, the H22 hits peak hp at 6800rpm... so no worries about ever having to reach 8500rpm without significant motor buildup anyways.
besides, redline is set to prevent valve float. that's a given. the peak hp in the H22A comes in at 6800 rpm... this is due to the cam profiles, as the head only breathes efficiently to 6800rpm. higher than that and you get a significant dropoff in power due to breathing difficulties.
as i understand it... reving above 6800 is not a "significant dropoff" in power, the power band simply levels off, and the "peak" HP is achieved at 6800. the engine still makes power throughout the entire rpm spectrum... above and below the peak HP.
at rev limit the power should drop "significantly".
as far as rev limiting, the only major danger to doing so, is heat buildup in the head and pistons etc.
since honda achieves max rev control thru the use of a fuel cut-off system. when the engine reaches rev limit you now have a 70 pound crankshaft spinning at a high speed (7800 rpm), and then the ecu cuts the fuel, but the crank is still spinning so its still sucking air, and now you have an excessively lean system that is burning really hot. this sudden increase in heat can cause damage to a number of different engine internals and systems.
if the bearings fail supposedly due to rev-limiting than they were never correctly installed, or more likely incorectly "seated" when the was engine broken in.
correction rephrase:
the h22a crank in most cases, IS safe to 8500 rpm
this includes bearings, and the crank itself
dont forget that no american V8 car companies balance their cranks at the factory, they are only balanced within LIMITS.
~boomer