Hi. My Corolla is making a loud tap/knock noise at high RPMs. I can't say what range since I don't have a tach. If the car is in park and I rev it up, i can hear it on the belt side of the engine. When I am driving, I can only hear it when it goes to shift gears. It's like a rapid tapping sound. It last for a few seconds until it shifts up to the next gear. I am stumped on it. I changed the oil when i first noticed it and it came out black as tar. The new stuff is staying clear so I not sure what caused the oil to turn black. Any help would be greatly appreciated. Brother said it could possibly be timing chain guides maybe, but I'm not sure how to check it. Here is a video of the sound. I noticed the tapping isnt as loud in the video, but it's definitely a heavier sound to it in person. I'll try tomorrow after work to get a clearer capture of the sound.