Try tightening-up on the exhaust manifold bolts to see if they are loose. As I get older and my hearing gets worse, it's harder to tell which direction a problem noise is coming from. E-brakes on. Jack up the truck, use jack stands. Transmission in neutral and start engine. Crawl underneath and listen. See if it's louder underneath. If not there, start over again. Moving your head as you listen can help. Get someone else to listen preferable one with younger ears than mine. If you still can't figure it out, very slowly pour something like Marvel Mystery Oil down the carburetor of your running engine. See if there is smoke leaking out other than the tailpipe.
Last edited by buoymaker; 01/21/20213:14 PM.
"Adding CFM to a truck will only help at engine speeds you don't want to use." "I found there was nothing to gain beyond 400 CFM."
