help diagnose whining noise

-
Another possibility, as in post 17: Check all the hoses to/from the heater controls, the vaccum control itself, and all the vacuum actuators for the heat and defrost doors. That is all vacuum operated; the vacuum control switch is on the back of the heat control panel, and the door acurators are around the heater box area.

I have heard similar whistles from air cleaners.
 
TrailBeast said:
That is a vacuum leak or intake sound if I ever heard one. (some carbs can whistle)
Listen how the tone changes with throttle opening, and goes away at WOT.
Click to expand...

You are correct. It's coming from the carb. I sprayed carb cleaner evetwhere and it didn't change. Can't get it to do it as bad while under the hood but it's definitely coming from the carb.

Any ideas on what could be done?

750 Holley street hp with phenolic 1" 4 hole spacer.
 
Take the carb off,, and check both of the base gskts to make sure they don't leave a small gap somewhere,, or somewhere that the gskt will suck in with high vacuum,, and close at low vac.. (wot)...

Tighten the carb base-plate screws on the bottom.. then try it again..


It may also be an internal carb/gskt leak..
 
inertia said:
Take the carb off,, and check both of the base gskts to make sure they don't leave a small gap somewhere,, or somewhere that the gskt will suck in with high vacuum,, and close at low vac.. (wot)...

It may also be an internal carb gskt..
Click to expand...

That is the first thing I'd be looking at (loose carb body or internal gaskets)

Just for kicks you might want to disconnect ALL vacuum lines from it and see if it still does it before you tear into it. (Brake booster and all if you have one)
 
Took the carb off. All bolts were tight. Took base off. Internal gasket looked good. Tried 1/4" gasket. base looks warped.

Download-File

Download-File
 
Leave the spacer out, install with both gskts,, and DO NOT over tighten, as the base plates are easily broken,, smear a little heavy grease beween the 2 gskts, - and the mating surfaces to help seal,, and later sepatate them.. check surfaces for irregularity,,

Is it possible the new carb studs are too long, and not tightening enuff,,
 
I agree, it sounds some sort of vacuum related. Nothing under hood can be heard ? Magnumdart had a good point about the radio memory wire, even without the power to radio that still is hot, have you taken the fuse out of both the radio and memory wires just to rule that out?
 
I've got it to make the noise while I was under the hood. It is defenitly coming from the back of the carb. It makes the noise constant after its warmed up at highway speed. By the time I pull over and yank the air cleaner off it goes away. Only to be heard as a little squeak when the throttle is blipped and the rpm's are falling.
 
skep419 said:
I've got it to make the noise while I was under the hood. It is defenitly coming from the back of the carb. It makes the noise constant after its warmed up at highway speed. By the time I pull over and yank the air cleaner off it goes away. Only to be heard as a little squeak when the throttle is blipped and the rpm's are falling.
Click to expand...

That SOOO sounds like a gasket.
(changes with throttle, temp AND high vacuum)
 
I had a whining noise in my car, then when my wife got out it went away.... Coincidence???
 
Are you sure you don't have a vacuum port open..?? plug blown off..

You need to invest in one of these stethescopes,, the cool thing is,, if you unscrew the "needle" section,, the "cone" that remains act like an old trumpet ear phone,, you just point the cone at the engine,, move it around till you find the direction of noise,, then just follow the cone to the noise,, in this case, the whistle..

Attach the needle, and you can place it against the outer case of diff or axle bearing, water pump,, and actually hear the bearings tuning,, and can really hear a bad bearing..

http://www.amazon.ca/dp/B0002SQYSM/?tag=fabo03-20

It's a "Lisle" avail at any parts store..

Less than $20,, will be one of best $20's you spent..


Detailed Description

Dual Purpose Set Detects Both Mechanical and Air Induced Sounds. Use the black diaphragm chamber and screw-in metal probe to detect mechanical sounds from bearings, engines, transmissions, etc. For air induced sounds, attach the vinyl hose to the hollow tube and funnel assembly. The funnel amplifier will detect noises from vacuum leaks, exhaust leaks, air leaks and wind noise. For hard to reach locations, remove the funnel and use the hollow tube.
 
I agree that is sounds like a vacuum leak. Gets louder as the vacuum goes up. Possibly inside the car itself and not under the hood. Heater control? Vacuum gauge?
 
its definitely coming from the carb.
Going to be trying the 3rd one tonight. 2 holley's do the same thing.
 
How long has this been going on? Maybe you could pull the plugs and check for a vacuum related lean burn condition.
 
I can't honestly say when it started or what triggered it. (been going on for awhile)
 
also cranked up the idle speed screw and took it for a test drive with the idle screws blocked off. no change.
 
I figure I would try an edelbrock I have laying around before I pull the intake off. Talked to holley tech and he stated that all intake leak noises will come through the carb.
 
After three carbs, if that is really where the noise originates, I would look elsewhere. Maybe a crack in the intake, stud not holding tight, etc.
 
There's a recent thread with an Eddy tech suggested dual 4's on a small block to cure an overheating (?) I believe..

Did you ever take the spacer off??

Before you go pulling the manifold,, I'd be scrutinizing the base/adaptor gaskets REALLY closely..

I can't re-enforce how strongly I recommend that $15 stethescope to pinpoint the noise to ground zero.. (THE noise)

Does the spacer and gskts match both the carb base and manifold, ie.. If you have an open plenum manifold ,, and a four hole spacer does the gskt overlap the edges enuff,, or are they loose to "flutter" under the spacer,.. ?? hope that makes sense...
 
You must log in or register to reply here.
-

Back
Top