Pesach Questions

My stove-top grates extend over the whole range, and there are large parts that will not be touched by flames if I kasher on the stove-tops . Placing them in a self-cleaning oven cycle will damage the grates and can also cause a fire (too much metal generating too much heat in the oven, according to what I read). Can I kasher the grates at 500 for an hour (or something like that) rather than self-cleaning? Other recommendations or thoughts? 

Typically, stove-top grates are assumed to instantaneously self-kasher, as drippings from the pots above, burn up immediately. We extend this assumption to the entire area of the grate where a pot would typically sit.  (Note: we have nonetheless developed the proper custom of cleaning and burning the grates for 10 - 15 minutes for Pesach. ) If your grates extend beyond the circle where a pot would typically sit, and you do not want to put them into a self-cleaning oven, I'd recommend covering just those parts of the grates with tin foil, in the same way that we cover other parts of the stove top that are beyond the area where the flames burn. 

RYK