i would pull the timing cover 1st and check around in there. mine lasted about 4 years but we sort of ignored the timing bounce of 3-5 degrees not good. it ended up right before we pulled it out it started jumping 15 degees !!!!!!!!!!!!!!!! how hard do you drive it? what kind of fuel do you use. how long did it take the knock to go away? you may want to pull the pan and do a bearing check. my motor didnt have 500 miles on it and it spun the bearings and i only raced it maybe 8 times total of 50 passes maybe? how high do you spin it?............... another thing you can do before you pull the pan is cut your oil filter open and examine it for gold glitter thats copper which means your bearings are not doing to good.