Identify this noise

[99'Subourbon]

Hey everyone, as continued discussion from the tune thread, here is the noise my engine makes. Let me know what you think it is.

Vortec 350 Motor Noise - Lifter Chatter?: https://youtu.be/ObDTwCXOdhk

 

[99'Subourbon]

A Jackass posting when he is drunk; good times.

 

[Parentnoia]

Sorry, I just saw this. While I cant pinpoint the source for you, I can tell you that I just had a minor noise similar to this except mine was more of a chatter where yours is more of a thunking. Mine wound up being low on oil (because it overheated one time and I may have burnt off some oil). I would actually ball park it as worse than lifter chatter and think it was a valve hitting the piston. I cant really tell from the video since revving it masks the sound on my end so I can tell if it increases or decreases with throttle. It definitely isnt simple lifter chatter, that's for sure. It's a solid-er sound.

 

[df2x4]

It definitely isnt simple lifter chatter, that's for sure. It's a solid-er sound.

This was my first thought as well, however it's pretty hard to tell from that video and I didn't want to be a negative nancy for no reason.

 

[99'Subourbon]

In person, the sound is hard to explain... It's like a harmonic wobbling?? And it is in sync when the motor intermittently shakes/vibrates (that sound worse than it is).

Regarding throttle and its occurence, I don't hear/feel it while giving it throttle, but it immediately does it momentarily soon as I let off the throttle. Whether at idle, or letting of the throttle, is occurrence/sound is always pretty subtle though. You can't hear it with the hood closed.

I'll try to take a better video, of once the engine is warmed up, so that the sound of the clutch fan isn't overpowering everything else.

 

[99'Subourbon]

Had my father in law over yesterday (Been a mechanic for over 40+ years, and builds modified and midget race cars), and let him listen to the noise. We found out its actually coming from underneath, and he thinks its either the water pump, or bearings somewhere in the drive assembly.

I am going to get it up to operating temp this weekend, then take the drive belt off, and fire her up (only momentarily, lol). If the noise goes away, then at least I know where to start looking. Oddly, when I am in drive, and I stop at a light or something, I hear a gurgling sound coming from under the hood, which makes me wonder if its a coincidence with potentially the water pump going out.

I'll keep the post up to date as I find stuff out.

If anyone else has any input, it's appreciated.