I'm about 30 miles from you, and I've been listening to engine noises for 50+ years. Drop by my shop sometime, and I'll try to help out. I'm the auto mechanics instructor at McGavock High School in Donelson.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!