Well, no matter how long you spray it, it will always hurt the engine. Build up your internals and a 75 shot will be safe...Talk to wildbillhtachbac for more info, who I beleive has a ZEX system in his 5th gen hb.
A friend told me that the motors that come with vtec heads are built to withstand the rigors of high RPM usage. He says that you have to put money in the head (valve springs and such) to support high rpms. I want to port the head and eventually put in bigger than stock cams. The desktop dyno predicts my engine will make power until 8500rpms. Is this pushing it? what will i have to do to support this? if i cant use nitrous till i build a motor, then i guess that'll have to wait.