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1970 Volkswagen Beetle H30/31 Carburetor Jetting
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boom10ful
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PostPosted: Sun Jun 17, 2018 8:47 pm    Post subject: 1970 Volkswagen Beetle H30/31 Carburetor Jetting Reply with quote

Hey all,

I bought a new Solex H30/31 to replace the old one that was on there. The old one had the stock 120 main and 50 idle jet. I rejetted the new one to have a 125 main jet and a 55 idle jet. The new carburetor had the 50 jet on the side of the carburetor and the 65 jet at an angle. I keep reading about how the idle jet is on the angled side and some say that its on the flat side. Which is the correct one?
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glutamodo Premium Member
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PostPosted: Sun Jun 17, 2018 8:58 pm    Post subject: Re: 1970 Volkswagen Beetle H30/31 Carburetor Jetting Reply with quote

They are actually BOTH part of the idle circuits. For precise emission control, VW split the idle circuit into the two separate pathways for the 30PICT-3 carburetor. And the H30/31PICT is a sort of bastardized clone of the 1970 1600SP 30PICT-3 mixed with the 1971 1300DP 31PICT-3.

These carbs have dual "enrichment" (power fuel) jets so a huge main jet isn't really that necessary, as there are TWO outlets built into the top half of the carburetor to handle high speed enrichment.

yes, 65 angled, 50 on the side.
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Cusser
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PostPosted: Sun Jun 17, 2018 9:56 pm    Post subject: Re: 1970 Volkswagen Beetle H30/31 Carburetor Jetting Reply with quote

boom10ful wrote:
The new carburetor had the 50 jet on the side of the carburetor and the 65 jet at an angle. I keep reading about how the idle jet is on the angled side and some say that its on the flat side. Which is the correct one?


On the H30/31 carburetor, there are two brass jets on the right side (right is right of car). The angled one (points slightly towards the rear of the car) is the idle jet (should be the 50). The other one (pointing straight out to the right side of the car) is the power jet (should be the 65), which feeds additional fuel at high throttle/high rpm. The power jet is needed to correct a tendency for the air correction jet to work TOO well at max airflow - it leans the mixture off too much and the power jet corrects this.
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Frank Bassman
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PostPosted: Sun Jun 17, 2018 9:59 pm    Post subject: Re: 1970 Volkswagen Beetle H30/31 Carburetor Jetting Reply with quote

Two different answers. So which one is it? I'm inclined towards 65 angled as that is how it has worked for ME and other cars I have seen.

-Frank
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boom10ful
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PostPosted: Sun Jun 17, 2018 10:01 pm    Post subject: Re: 1970 Volkswagen Beetle H30/31 Carburetor Jetting Reply with quote

Cusser wrote:
boom10ful wrote:
The new carburetor had the 50 jet on the side of the carburetor and the 65 jet at an angle. I keep reading about how the idle jet is on the angled side and some say that its on the flat side. Which is the correct one?


On the H30/31 carburetor, there are two brass jets on the right side (right is right of car). The angled one (points slightly towards the rear of the car) is the idle jet (should be the 50). The other one (pointing straight out to the right side of the car) is the power jet (should be the 65), which feeds additional fuel at high throttle/high rpm. The power jet is needed to correct a tendency for the air correction jet to work TOO well at max airflow - it leans the mixture off too much and the power jet corrects this.


The weird part is that both carbs old and new had the 65 jet on the angled side.
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glutamodo Premium Member
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PostPosted: Sun Jun 17, 2018 10:03 pm    Post subject: Re: 1970 Volkswagen Beetle H30/31 Carburetor Jetting Reply with quote

You bloody well said "power jet" and that is TOTALLY WRONG. It has NOTHING TO DO WITH ENGINE POWER. As I already said, the idle and transition circuits were split into two pathways, the main one and the additional (or auxiliary one) and those are NO WHERE NEAR GIVING THE ENIGNE ITS HORSEPOWER. VW called this the "excess", "additional' or "auxiliary" jet, but it has NOTHING TO DO with giving the engine more power, it has to do with fine-tuning the idle circuit for emissions control.

The high speed enrichment, or "Power Fuel Jets" are in the TOP HALF of the carburetor and they only come into play at high engine speeds (where they DO deliver "the juice" for the top end engine output)
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Cusser
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PostPosted: Mon Jun 18, 2018 7:46 am    Post subject: Re: 1970 Volkswagen Beetle H30/31 Carburetor Jetting Reply with quote

From http://www.vw-resource.com/jets.html#30

"On the H30/31 carburetor, there are two brass jets on the right side (right is right of car). The angled one (points slightly towards the rear of the car) is the idle jet. The other one (pointing straight out to the right side of the car) is the power jet, which feeds additional fuel at high throttle/high rpm. The power jet is needed to correct a tendency for the air correction jet to work TOO well at max airflow - it leans the mixture off too much and the power jet corrects this."

"The idle jet is usually a size 55 (when the main jet is normally a size X125 or X127.5) but it might be a size 65 if the main jet is a X122.5 or smaller.

The power jet is usually a size 65. In most cases you can just leave the power jet alone. It only works at full throttle and high RPMs ? the size 65 power jet should work fine for those conditions."
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joey1320
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PostPosted: Mon Jun 18, 2018 9:00 am    Post subject: Re: 1970 Volkswagen Beetle H30/31 Carburetor Jetting Reply with quote

I went through this last year. Cusser helped me out.

https://www.thesamba.com/vw/forum/viewtopic.php?t=684640&highlight=
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glutamodo Premium Member
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PostPosted: Mon Jun 18, 2018 9:00 am    Post subject: Re: 1970 Volkswagen Beetle H30/31 Carburetor Jetting Reply with quote

Okay, just show me some kind of factory documentation that indicated that "claim" - Oh, wait I can show you such that shows it totally part of the idle circuit. They can call it that whatever they want.

It's NOT power in any way.

It. Is. Part. Of. The. Idle. Circuit.

Image may have been reduced in size. Click image to view fullscreen.


Image may have been reduced in size. Click image to view fullscreen.


Image may have been reduced in size. Click image to view fullscreen.


Whatever feeble flow that "might" occur through that at high RPM is NOTHING compared to what goes through the intended high speed "enrichment" jets, ("power fuel" system)... And THESE are the dual Power Fuel Jets as seen on 30PICT-3 and newer carburetors:

Image may have been reduced in size. Click image to view fullscreen.

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IMAGE NOTE: It has been noted that Chrome based browsers may have issues in displaying my vast image library, which use non-secure links and are on an FTP server. Images should still be viewable if the link is clicked though.
I do not know how to fix this. All I can say is it all works fine for me with what I use, Firefox.
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