Whistle noise

[Goldbull]

I have a 1974 c10 with a 292. My question is. Why does it make a whistle like noise from the carburetor when I accelerate. If y pass the 2000 rpm it stops. At times it sound like if it had turbo system but everything is stock.

 

[Obwonkonobe]

Vacuum leak, try spraying carb cleaner very lightly around common leak places and see if it accelerates, if it does that's your leak because it sucks it in. Just be EXTREMLY careful and watch for flames, have an extinguisher. Also be sure all the little outlets on the carb are plugged if they're not used

 

[1987 GMC Jimmy]

Those little aftermarket one way check valves for the A/C and cruise will whistle, especially when you shut down the truck or car. They’re not made very well...

 

[Obwonkonobe]

Those little aftermarket one way check valves for the A/C and cruise will whistle, especially when you shut down the truck or car. They’re not made very well...

Do they go between your manifold and the vacuum resovior? Is it required? I don't have one

 

[1987 GMC Jimmy]

Do they go between your manifold and the vacuum resovior? Is it required? I don't have one

Yep. One side goes to HVAC control, and the other goes to the vacuum reservoir and then the cruise servo from there. I don’t think it’s 100% necessary like a brake booster check valve, but I assume its presence helps keep the A/C from randomly dumping air somewhere else or the cruise servo from disengaging when engine vacuum fluctuates (i.e. when accelerating).

 

[Obwonkonobe]

Hmph, that may explain why my a.c. isn't always 100%, could you find me a picture so I can try to find one?

 

[1987 GMC Jimmy]

It’s Dorman 47150. All the parts stores have them on the shelf. It took me three tries to find one that held vacuum properly. They are not well made, at least not consistently.
I tried to upload a picture, but it wouldn’t let me. There’s also AC Delco 15-50568, but I haven’t tried that one.

 

[Obwonkonobe]

It’s Dorman 47150. All the parts stores have them on the shelf. It took me three tries to find one that held vacuum properly. They are not well made, at least not consistently.
I tried to upload a picture, but it wouldn’t let me. There’s also AC Delco 15-50568, but I haven’t tried that one.

Thank you a ton, I'll get on that

 

[436'd skylark]

A collapsing vacuum hose will squeal like crazy too.

 

[1987 GMC Jimmy]

Thank you a ton, I'll get on that

You’re welcome!

 

[Goldbull]

Ok. Checked all connections and vacuum everything seems ok. The whistle is made inside the carburator

 

[1987 GMC Jimmy]

Silly question, is your breather lid upside down?

 

[Goldbull]

No. I’ll try to get a video when I get off work.