What the hell is this noise??

[Slash]

I think I asked about this before, but I finally found a video PERFECTLY replicating my issue. It can't get more exact.

At the end of this video, you'll notice durring revs his carb makes a sucking/whistleing noise. What causes this? It should be noted it runs strong, lacks no power and there are no vaccuum leaks or any leaks, period. I have been told by several reputable people nothing is wrong, that its supposed to be like that. I've also been told the carb is too small which is not the case, 650cfm is more than enough for a a 351W application. I was also told it could be how the air flows at a certaim cfm, which seems logical, but no one said what it is or what causes it. As I said, everything is sll good, its just there. Also, as shown, occurs at idle only. You won't hear it when driving. I have had the issue in my truck since the motor was rebuilt.

 

[Dean]

Hm... My parents car actually have the same sort of noise. But, sadly I can't help you with what's making it.

 

[Tyger]

Isn't it literally just a whistle sound? Any air or gas forced through a certain shape/size of aperture at a certain pressure can cause a whistle sound, same as sometimes when someone has a blocked nose, it whistles when they breathe through it, or if you blow over the neck of a bottle at a certain angle, you get a sound.

 

[Slash]

I'd think it'd be something stupidly obvious but it's quite annoying and extremely loud, loud enough for a cheap phone to pick up clearly and drown out the motor. What your saying kind of goes to back to a certain cfm though. I was always thought something might be wrong so I was stumped.

 

[Tahli462]

The transmission, or its probally the fan.

 

[Slash]

Wait, what? Those have nothing to do with this as it's clearly a carb issue.

 

[zedextreme8177]

Intake noise, probably caused by drawing a large amount of air through a small hole. This is clearly heard in the Daytona 675 (fuel-injected, but apparently draws air through a very small hole):


And in these carburetors as well:


It should not be an issue as far as I know, just some aerodynamics at work

 

[Dennisch]

Might want to check if the seal between the carb and intake is still in one piece, or that the carb sits perfect on the manifold.

Press down on your carb when revving the engine, if the sound goes away, you have a faulty gasket. If it doesn't go away, it must be something else.

 

[Slash]

Might want to check if the seal between the carb and intake is still in one piece, or that the carb sits perfect on the manifold.

Press down on your carb when revving the engine, if the sound goes away, you have a faulty gasket. If it doesn't go away, it must be something else.

Both gaskets are there and brand new, one for the 2" spacer and one underneath and each bolt is correctly torqued. We are using a 1969 Boss 302 4bbl intake modded to fit, so what was said about forcing air through a small hole might be true.