7.3 idi knock

Sorry, i know this has been asked before, but every thread i’ve found relates to a specific maintenance action and reaction, whereas my knock has been going on for a bit
With that being said,
7.3 idi with the zf5. Injectors and pump are <2 years old. Rockers are in torque spec, 40ft lbs.
knocks, increasing with rpm and hard to hear/gone after 1500-2k rpm
Using a stethoscope, I listened to the injectors, they all made that crisp click except for the back two on each side, sounded more like someone hammering a nail in a board, but they both sounded the same so i guessed it was normal
Knock was louder with scope on cylinder head, no knock whatsoever when i scoped the oil pan and bottom of block, so im pretty sure its not a rod.
Im thinking it may be the back injectors, i just dont know how they should sound really, never heard a perfectly good idi running before in person, mine has been a project and half the time i wonder if the strange stuff i hear is normal or not, anything helps thanks!
Good oil pressure btw just installed a mechanical gauge, shows 22-27psi

Is it making chuffing or popping noises in the intake or exhaust listen with the air cleaner off. Next I want you to loosen injection lines at the injectors one at a time this is a manual cylinder cut out if/when you find one that changes or makes noise go away swap that injector with another hole then start it back up and repeat the cylinder cut.

Where were the injectors and IP from?

hacked89 said:

Where were the injectors and IP from?

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Ip is a reman 5028 from dieselogic, previous owner replaced the injectors and return lines idk where from

Isaac Ristow said:

Is it making chuffing or popping noises in the intake or exhaust listen with the air cleaner off. Next I want you to loosen injection lines at the injectors one at a time this is a manual cylinder cut out if/when you find one that changes or makes noise go away swap that injector with another hole then start it back up and repeat the cylinder cut.

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I’ll do that today, thank you!

So, this is what i found. Not sure of what to think of it. Seems like its coming from the drivers side, i guess.

Isaac Ristow said:

Is it making chuffing or popping noises in the intake or exhaust listen with the air cleaner off. Next I want you to loosen injection lines at the injectors one at a time this is a manual cylinder cut out if/when you find one that changes or makes noise go away swap that injector with another hole then start it back up and repeat the cylinder cut.

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With air cleaner off it sounds like a hollow knock, like a knock on a 2x4. Video shows, hard to make out though.

Your video to me, just sounds like the IDI in my 86. Don`t really notice anything bad.
I do hear a low womph womph or thump thump sound from the Air Cleaner. Pick up the RPM`s a bit and it goes away.
Hey it`s an old Diesel and they like me make funny noises till I get up and movin.


Goat

Thelebowski said:

With air cleaner off it sounds like a hollow knock,

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That's perfectly normal. I call it the intake pulse for lack of a better term. I have no idea why these engines make that sound, just that they do.

IDIBRONCO said:

That's perfectly normal. I call it the intake pulse for lack of a better term. I have no idea why these engines make that sound, just that they do

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Thats relieving lol. I appreciate you guys, sorry for being green about it. I guess if it cant be heard in a video its not bad or my minds just playing tricks on me. Other injector ping videos sound the same (high pitch wrench on a frame knock, not the intake noise) but way louder and easy to pick out, so i guess if it is really there then it’ll let me know eventually.

If it’s important it will get worse

It helps me to have someone else crack injector lines while I stand back and listen. Much easier to separate it from the rest of the noise.

Does your air cleaner still have the dome shaped resonator under the lid?
I think you’re hearing the intake reversion pulsation noise. The air cleaner incorporated a helmholtz resonator device under the lid to kill that intake noise. It was common for consumers to remove the resonator under the mistaken belief that the resonator hurt performance.

In fact, there is absolutely no performance effect other than increased intake noise, which gives the impression that the engine makes more po.

There is absolutely no fuel economy effect either.

My '87 6.9 n/a doesn't have one. Are they available to buy?
Sound like a cheap way to cut down on some of the noise in the cab.

They are spot welded to the bottom of the air cleaner lid on N/A engines. The ones that didn't have that, had a piece of metal that went across the opening for the intake manifold and had a hole for the lid hold down bolt to go through. There may have been another set up, but I don't remember it. I don't remember seeing the "baffle" and the piece across the bottom together. Why it wasn't on all of them, I have no idea. In order to get one, you'd have to find a lid with that already on it.