Wth is causing this squeal?

Before I pulled the motor, I'd probably pull the valve covers and look it over. I'd also still pull the oil cap off with it running just to give it a listen and see what happens.

I am very interested in discovering WTF this noise is!
 
If you barely blip the throttle or even hold it slightly open, does it go away or change pitch?
I'm leaning towards a vacuum leak myself.

Currently listening to your video repetitively here at the el Amigo Taco truck while the lady inside is wondering where the whistle was coming from.
 
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Jody Treadway said:
If you barely blip the throttle or even hold it slightly open, does it go away or change pitch?
I'm leaning towards a vacuum leak myself.

Currentlylistening to your video repetitively here at the el Amigo Taco truck while the lady inside is wondering where the whistle was coming from.
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It gets louder
 
justjeepin86 said:
It gets louder
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Rotationally faster or just louder?

Pic for verification purposes
PXL_20250925_175954193.jpg
 
justjeepin86 said:
I'm heavily leaning towards lifter. I'll do some listening with a screwdriver this afternoon. Trick is to not run it much more, jic.
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I also think lifter. The roller tip has a tendency to fail and make noise. Great time to do a cam swap...

:edit to add I sent the video to a friend who also is saying lifter.
 
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Croatan_Kid said:
With it running and making the noise, pull the oil cap off and see if it stops. If it does, there's some PCV hoses routed incorrectly. Wouldn't show as a vacuum leak, but it'll put a helluva lot of vacuum in the crankcase and find the easiest seal to pull air past. That'll make some weird noises.
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Well, @Croatan_Kid wins the internet. Effing crazy.

It's been idling for 30 min.

Shame I didn't try this before I took it a part. But it won't cost but a little atf now. Well, and I have to tune up the pcv system.

 
justjeepin86 said:
Malbrittan mentioned a vacuum leak. Could this really be coming from one? I'm gonna be pissed and happy if that was the case.
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Hell, I’m just making shit up, don’t listen to me. 😁

Listening to the later videos, it’s rhythmic. A vacuum leak would be constant.

I vote stethoscope/tube to narrow down where it’s coming from.
 
Back to being serious.

Years ago Bill Carver (44Magnum) told me to be careful putting hoses on connections. He has seen them tear a flap inside the hose and cause vacuum flow issues that you can’t see or find from the outside.

I say that since you said you ran propane around the outside with no luck of detection and the fact that it was rhythmic. Just makes me think the leak or plug is opening and closing to give you that rhythmic sound.
 
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