Whistling holley 1920

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hosehead

hosehead

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So I have a new(to me) 68 dart with a 225 and the carb whistles. It's annoying!:D. I have replaced the base gasket, sprayed carb cleaner all over it to see if the idle changes etc. The whistle is definitely coming from inside the carb. So today I took the carb off and turned it upside down and I noticed there is a hole drilled in the throttle plate. In all the pictures of holley 1920's I can find there is no extra hole. Is the hole supposed to be there? Do you guys think that's where my whistle is coming from? Do any of you guys have any insight into my situation before it slowly drives me insane?? Seriously, any help is greatly appreciated. It really is annoying. Thanks all.:prayer:
 
You can weld or rivit that hole closed, as it is not factory and probably where the whistle is coming from.
People do that to a carb because the cam they used needs more air to idle higher and stay running.

You might use a small screw and nut if it will clear everything, but I would'nt use that method unless I peened it down or locktighted it so there would be zero chance of it coming loose and going into the motor.

My original carb had strange issue's when I first got the car and it took awhile to find out someone had drilled two holes from the outside of the carb base to under the butterflies, basically for the same reason but UNFILTERED air???
Some peoples kids, ugh.
 
Thanks trailbeast. I figured the hole wasn't original. It's weird that someone drilled it there when the carb is on a totally stock slant 6. I'll look for a replacement throttle plate as I really don't want anything falling into the motor.
 
If you have trouble finding another one, you can plug it by threading in a small, shortened brass screw and then stake in the other side.
 
hosehead said:
Thanks trailbeast. I figured the hole wasn't original. It's weird that someone drilled it there when the carb is on a totally stock slant 6. I'll look for a replacement throttle plate as I really don't want anything falling into the motor.
Click to expand...

Holley actually makes throttle plates with the hole in it. Not sure if yours is original, or someone else drilled it. If your car is running/idling good, I would drive it for now. Installing a screw ect will work, but that would suck, litterally, if it was to come out.
If it is bothering you to no end, then start looking for a replacement throttle plate.
Whether its from a vendor, or someone on the site. Google is always good ! :)
 
Yes a loose screw would suck, but staked in screws are how the throttle plates in many (most?) carbs are held into the throttle shafts anyway. Brazes or welds would work unless it is on the side of the plate that has to slide out through the throttle shaft slot if you ever wanted to completely diassemble things. A 'no-hole' plate would be best, but you are going to have to re-stake in the retaining screws.

Just as info, BTW, my Holley 1920 does not have a hole in the throttle plate....
 
My Holley does the same after I rebuilt it can’t figure out where it’s coming from exactly but it’s from within.

I would suspect the economizer diaphragm as that top already looked quite malformed (and the new diaphragm is a tad thinner). It does sound more internal though.

It runs much, much stronger since rebuilding and doesn’t seem bothered with it, so for now it’s good (and I’m swapping to a Carter anyway).
 
TrailBeast said:
You can weld or rivit that hole closed
Click to expand...
Don't do this.

TrailBeast said:
as it is not factory
Click to expand...

Is too. Some year/spec 1920s closed the throttle plate completely for curb idle and metered air through that calibrated hole instead.

TrailBeast said:
and probably where the whistle is coming from.
Click to expand...

No, the whistle is likely from one of the air bleeds.

TrailBeast said:
My original carb had strange issue's when I first got the car and it took awhile to find out someone had drilled two holes from the outside of the carb base to under the butterflies, basically for the same reason but UNFILTERED air?
Click to expand...

If those holes were truly to the underside of the butterflies, then yeah, that's a no. But if they were these kind of holes (start at linked post and keep scrolling down for documentation), they were put there at the factory for a good reason, and they were supposed to be there.
 
RustOnWheels said:
My Holley does the same after I rebuilt it can’t figure out where it’s coming from exactly but it’s from within.

I would suspect the economizer diaphragm as that top already looked quite malformed (and the new diaphragm is a tad thinner). It does sound more internal though.

It runs much, much stronger since rebuilding and doesn’t seem bothered with it, so for now it’s good (and I’m swapping to a Carter anyway).
Click to expand...
Does it sound like this?



Jim
 
hosehead said:
So I have a new(to me) 68 dart with a 225 and the carb whistles. It's annoying
Click to expand...

Often fixable with some carburetor cleaner spray; with the engine running at a fast idle, put the end of the straw on the larger of the two air bleeds facing the sky, visible by looking down into the carb throat, and spray. Then repeat with the smaller air bleed. Once that's done, adjust the ignition timing—yes, it —and the idle speed properly (not by guess-and-golly). On carbs like this, with the throttle plate hole, the throttle plate is meant to be fully or very-almost-fully closed at curb idle. You set the mixture as described here, (the idle speed instructions there are for carbs without throttle plate holes), and you'll also find carb operation and repair manuals and links to training movies and carb repair/modification threads at that same link. If your '68 has the distributor vacuum control valve, that has to be adjusted correctly as well, or you'll get weird problems which can include difficulty getting the correct idle speed and (yep!) whistling at the carb.

hosehead said:
there is a hole drilled in the throttle plate. In all the pictures of holley 1920's I can find there is no extra hole. Is the hole supposed to be there?
Click to expand...
Yes, it is. In the '68-'69 timeframe, all the US carb makers were starting to transition away from the old method of cracking the throttle plate open a bit to provide idle airflow; instead they went to consistent, fixed idle airflow by closing the throttle plate completely at idle and providing a calibrated hole in the throttle plate, or no hole in the throttle plate but an adjustable idle air bypass pathway in the carb body as shown here:

Throttle-closed-idle.jpg
 
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ProjectBazza said:
Does it sound like this?



Jim
Click to expand...

This is the sound:



It’s a high pitch and an occasional extra squeal which makes me think there is just a little too much room at a mating point between a diaphragm and a mating surface (like a balloon passing air when you stretch it).

I have baselined the carb by turning the idle mixture screw 1.5 times out and the idle speed screws - from the top of my head - 2.5 times in (according to Uncle Tony’s advice). I didn’t have the time to optimize idle screw with warm engine.
 
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Well, @slantsixdan is an expert, so I would certainly listen to him. I do, however, have one more suggestion. Was the car idling fine? If not, there could be a slight air leak somewhere. Look for something that is loose. I had a friend with a Volarie SW with a slant 6, It was idling poorly, and making a sucking/whistling noise. I took the carb off and found that the bottom plate of the carb was slightly loose, I gave each of the 4 screws on the bottom about 1/2 turn, and everything was fine.
That is all I've got.
 
RustOnWheels said:
This is the sound:



It’s a high pitch and an occasional extra squeal which makes me think there is just a little too much room at a mating point between a diaphragm and a mating surface
Click to expand...


Remove the hose that goes to your choke pull-off, at the carburetor body end. Plug the nipple on the carburetor. Start the car. Still whistling?
 
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The car is idling fine and running strong, without tuning the carb again even. I know UTG is debated and I read the links from slantsixdan and they are very, very useful, thank you! I’ll also check the choke pull-off. Thanks again, Dan!

The engine isn’t at its prime as one can hear (there is a ticking sound which I’m not sure if it’s from a lifter or only the big crack in one of the exhaust manifold legs) and I haven’t did a lot of work on it except changing the oil, filter and coolant since I got it home. A few weeks ago the carb suddenly decided to break down so I rebuilt it. After the first test run I didn’t hear the squeal. When I turned it off and on later this sound came to be, or maybe I didn’t hear it the first time.



This was just after rebuilding, it scared me how fast it jumped to life (bowl was empty, I did not do anything with the gas pedal, just cranked it and it flew back to life in an instance).
 
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