1976 Fj40 2F Carb Vacuum Noise Diagnosis? (Video Included)

Ackcruisers

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I’m looking into to fixIng this whining sound on my 1976 2F. Please give it a listen and let me know what you think is the fix.

Pertinent Info:
-Chinese made H3662 carb
-Non USA small cap dizzy (Advace/Retard)

 
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Too shiny?

Sounds like a squealing belt or a bearing, to me... like alternator or AC compressor.

But, your video focuses on the carb-area and it sounds more focused around the carb. So, your title may be correct... vacuum leak.

I’m on an iPhone... I can’t see well enough, on this phone, to tell if you have any open vacuum ports.

Could also be a vacuum leak around the intake manifold.

I cant tell if you have an smog pump... if you do, see if it’s coming from there.

Have you sprayed carb cleaner, water, etc. around the carb/intake/vac ports/etc. and listened for idle change?

Failing identifying a vacuum leak, pull the valve cover and see if it’s louder and more focused.
 

77mustard40

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Sounds like a vac leak to me, I had that back in the day when I had a Webber. Screws for the adapter plate were too long and bottomed out before torque.

Is that a brand new carb install? Where does the sound come from? YouTube fails us without your input.
 

Ackcruisers

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Too shiny?

Sounds like a squealing belt or a bearing, to me... like alternator or AC compressor.

But, your video focuses on the carb-area and it sounds more focused around the carb. So, your title may be correct... vacuum leak.

I’m on an iPhone... I can’t see well enough, on this phone, to tell if you have any open vacuum ports.

Could also be a vacuum leak around the intake manifold.

I cant tell if you have an smog pump... if you do, see if it’s coming from there.

Have you sprayed carb cleaner, water, etc. around the carb/intake/vac ports/etc. and listened for idle change?

Failing identifying a vacuum leak, pull the valve cover and see if it’s louder and more focused.
Thanks for the suggestions, much appreciated. My 40 was never smogged as it was originally from Colombia. I sprayed water (with a slight mixture of dish soap) around the intake manifold. As soon as I sprayed water around the drivers side rear carburetor base plate mounting bolt (image below with red arrow), I immediately noticed an idle change. Shortly after, the noise was gone. The water apparently filled the void enough to stop the whine. This has ruled out the other possible sources of the noise (compressor, belts, bearings etc..)

Intuitively, my next step is to tighten mounting bolt to create tighter seal.

E8EAD6C2-E116-4958-954A-049D95AD2036.jpeg
 
Last edited:

Ackcruisers

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Sounds like a vac leak to me, I had that back in the day when I had a Webber. Screws for the adapter plate were too long and bottomed out before torque.

Is that a brand new carb install? Where does the sound come from? YouTube fails us without your input.
Thanks for weighing in. The carb was installed by the PO. It does appear to be new. I’m not familiar with these Chinese non-USA carbs (H3662) and am now doing research to get up to speed on best options. I may keep this carb as backup and go for a rebuilt Aisin. Wondering if there will be any performance improvements.
E4E48C6C-9047-42FC-B977-ADAEDDF741C2.jpeg
 

Ackcruisers

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Here is updated video after tightening mounting bolts. All 4 required more torquing.
No more vacuum leak sound for now. But how about those noisy valves? Will be adjusting those for the first time next.
 

77mustard40

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Thanks for weighing in. The carb was installed by the PO. It does appear to be new. I’m not familiar with these Chinese non-USA carbs (H3662) and am now doing research to get up to speed on best options. I may keep this carb as backup and go for a rebuilt Aisin. Wondering if there will be any performance
I don’t have anything to offer on the Chinese carb. I switched from a Holley (when purchased) to a Webber then ultimately to Aisin. I found a good core from a close model year (76 for my 77) and learned how to rebuild it from others’ MUD contributions. Sourced all the parts I’d need to make the switch then went for it.

As for performance... remember we are talking about a 2F here so I don’t think you are going to notice anything through the seat of your pants. Mine starts easily hot or cold, comes off idle smoothly and pulls ( I use that phrase generously) through the engine’s rpm band. To me that was my win.
 

Ackcruisers

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I don’t have anything to offer on the Chinese carb. I switched from a Holley (when purchased) to a Webber then ultimately to Aisin. I found a good core from a close model year (76 for my 77) and learned how to rebuild it from others’ MUD contributions. Sourced all the parts I’d need to make the switch then went for it.

As for performance... remember we are talking about a 2F here so I don’t think you are going to notice anything through the seat of your pants. Mine starts easily hot or cold, comes off idle smoothly and pulls ( I use that phrase generously) through the engine’s rpm band. To me that was my win.
Thanks for setting my expectations with the 2F. I do remember 26 years ago my 1969 F engine after valve job with Weber carb had decent power and acceleration. The H3662 carb I have now performs well at idle, does not stall, and accelerates as well as can be expected.
 
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