22re 1990

I have a knock that I can plainly hear when I am driving. It sounds just like a loose valve only a bit louder. It increases in frequency with rpms. It is not a bent valve and it is not a rod bearing. It is much higher pitched than a rod bearing. I have adjusted the valves at least 8 times and it makes no difference. With a stethoscope the sound is loudest at the exhaust manifold. I searched for a leak there and all down the exhaust and can find nothing. I can't hear it with the scope at the valve cover because the valve noise drowns it out. I can barely hear it from the bottom of the block. Other than that the truck runs great.

The noise seems loudest at 1500 rpms. I believe it increases in frequency above that so that it just blends in with sound of the motor. At idle it is noticeable but just barely.

As I said, the knock is the most noticeable when behind the wheel. If I turn on the air or heater, I cannot hear it. It's harder to hear when outside the car. Makes no difference if the truck is in gear.

Any ideas? Wrist pin?

 

Maybe post a video with the sound so we can hear it?

Sounds similar to a knock on a Dodge Durango I had a year ago. Scared me when it started making noise. Turned out to be a small leak along one of the header pipes.