Engine making a "knocking" sound and whistling from the exhaust. What things should i check?

[headhunter38]

As the title says, my truck has started making some noises. Its a 1991 f250 7.3 na. Here's a video put i together with what it sounds like

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I popped tested the injectors and they all tested at ~1600psi and had good spray patterns. I know that is really low but its not quite "bad" either. One of them i think had a leak and after ultrasonic cleaning it was gone. Reinstalling the injectors after cleaning got rid of a stumble/misfire coming off of idle. However the "knocking" and exhaust whistle were unchanged. I removed the valve cover and checked the rockers and pushrods. I pulled the pushrods from the cylinder with the leaking injector and they were still good. Ive tried using a mechanics stethoscope and havent found the source. I plan to get one of those timing adapters and check the timing. If that doesnt make a difference I plan to try shimming the injectors and or getting new ones. Is there anything else I should check? The engine doesn't vibrate so I dont think it's anything in the rotating assembly ( i hope). Also it doesnt smoke except when running the wmo blends and even then it doesnt smoke very much. Engine doesnt feel down on power either.

 

[Dirtleg]

Have you tried loosening 1 injector line at a time while running to see if it is indeed injector related?

When I bought my skid steer it had a bad knock. Thought it might be the bottom end initially. It was extremely obvious that it was injector related, not mechanical, and which cylinder when I disabled them individually.

 

[headhunter38]

Have you tried loosening 1 injector line at a time while running to see if it is indeed injector related?

Forgot to add that. Yes I did that prior to pulling the injectors and cleaning them. The sound didnt change when doing that. Can air intrusion cause this kind of sounds?

 

[ROCK HARVEY]

That whistling is interesting. I’ve heard “chirping” sounds from exhaust before that ended up being cracked exhaust manifolds, but that whistle is new to me.

Have you replaced the IP or anything between the video you recorded a year ago and now? It definitely sounded smoother a year ago, and I wonder if it’s timing-related.