[CAR75]

I race a 1/4 mile asphalt track. I have a stock head. 2" od pretty much straight exhaust with turbo muffler.I am hitting 6500-7000 rpm down the straight. I am runing 185/65/14 tires.Thinking on going to 195/70/14,which is the limit at the track. I now bent a valve for the second time since the end of last season.I tried to keep it around 6000 and just get passed like im standing still. Would a little better than stock valve springs help this?/ I really need some help to keep this from happening. Thanks