Carb "rings" can you change them out? (1 Viewer)

[OregonCruzer]

I vote in favor of changing the nomenclature "rings" to "almost spheres if it wasn't for the hole in the middle", which could then be shortened to "asiiwfthitm" for ease of speech.

 

[Mace]

The Webbers and other carbs with replaceable venturis typicaly use a set screw for retention.

The Aisin carb was most likely used on a variety of different rigs. Hence the need for multiple sizes of venturis. Also it is easier to make a base cast unit then tune it for the motor it is going on.

You may be able to track down the venturis but with those stamped into the housing I do not believe they ever designed them for replacement.

The Webers venturis can be tough enough to get out sometimes. I woudl suspect that even if you did get the "dents" reversed, they woudl be super stuck in there.

 

[FJ40Jim]

Do not call Aisin, looking for parts for an Aisan carb.
Aisin makes drivetrain components.

The venturis are not supposed to be serviceable.
But they can be removed and changed. The largest venturis used are the 31/35 seen in the pics. but it is possible to build a carb w/ 33/35 or even 35/35 if one were so inclined. The carb will work, as long as the venturis are smaller than the 38/40 throttle body.

The parts have to be sourced from other parts carbs, they were never available as service parts.

Common sizes are 28, 31, 33, 35mm.

 

[Mace]

There you go!

 

[FJ60Cam]

Run it without the rings

 

[SDFJ60JFK]

Jim C. said:
The venturis are not supposed to be serviceable.
But they can be removed and changed. The largest venturis used are the 31/35 seen in the pics. but it is possible to build a carb w/ 33/35 or even 35/35 if one were so inclined. The carb will work, as long as the venturis are smaller than the 38/40 throttle body.

The parts have to be sourced from other parts carbs, they were never available as service parts.

Common sizes are 28, 31, 33, 35mm.



What kind of performance increase will this provide?

I always thought he stock venturi size was 38/40.

I am under the (mistaken??)impression that the most airflow that can be provided is with the stock carb. IF a person was to put 2 35 rings in a carb. Would that mean that the weber 38/38 would have 2 38mm venturis leading to the engine VS the aisin haveing 2 35mm venturis. Thus allowing more airflow.

I must not be seeing the hole picture.

John
TLCA 6192

 

[beaufort-fj60]

thanks Jim...

 

[FJ40Jim]

Jim C. said:
The venturis are not supposed to be serviceable.
But they can be removed and changed. The largest venturis used are the 31/35 seen in the pics. but it is possible to build a carb w/ 33/35 or even 35/35 if one were so inclined. The carb will work, as long as the venturis are smaller than the 38/40 throttle body.

The parts have to be sourced from other parts carbs, they were never available as service parts.

Common sizes are 28, 31, 33, 35mm.

What kind of performance increase will this provide?

Somewhere between -30% and +15%. Depends on how the airpump underneath the carb is built.

I always thought he stock venturi size was 38/40.

Varies by year and market.
All 2F/3F carbs are 38/40 throttles.
Primary venturis are available 28, 31, 35.
Sec venturis are available 28,33 or 35.

I am under the (mistaken??)impression that the most airflow that can be provided is with the stock carb. IF a person was to put 2 35 rings in a carb. Would that mean that the weber 38/38 would have 2 38mm venturis leading to the engine VS the aisin haveing 2 35mm venturis. Thus allowing more airflow.

Stock FJ60 carb is almost the biggest that is readily available. 75-76 USA carb is biggest CFM available, around 425.

The weber 38/38 that is commonly sold as an upgrade has 38/38 throttles and 26/26 venturis.

By comparison Aisan 38/40 has 31/35 venturis.

Aisan throttle area: 23.90cm^2
Weber throttle area: 22.68cm^2
Aisan is 5% bigger.

The limiting factor to airflow through a carb has to be the venturi. For the carb to work right, there must be a significant delta P right at the venturi, a greater change than anywhere else in the induction system.

Cross sectional flow area at the venturi:
Aisan: 17.17cm^2
Weber: 10.62cm^2
Aisan has 61% more CSA in the critical venturi area.

A bionic 2F carb with two 35 venturis would have 19.24cm^2 of CSA.
An increase of 12% over stock.

I must not be seeing the hole picture.

Very punny.

 

[SDFJ60JFK]

Jim,

Great info.

So have you ever done a real world Bionic carb and was it really worth junking out another carb for the venturis??

Thanks for your expertise.

John
Lead SD

 

[beaufort-fj60]

Jim,

Great info.

So have you ever done a real world Bionic carb and was it really worth junking out another carb for the venturis??

Thanks for your expertise.

John
Lead SD

x2..


so if the Weber is "weaker/lame-er" how could your gas mileage decrease when using one. Are they less efficient? or is it just a figment of the imagination.

lol

 

[donny paradise]

If you want a carb that Hauls Ass get a Holley Thats what I have on my Thunder truck and it'll get 2nd gear scratch some what economical too

 

[cruiser88]

If you want a carb that Hauls Ass get a Holley Thats what I have on my Thunder truck and it'll get 2nd gear scratch some what economical too

What model # for the cruiser? I had a model # 2100 on my 40 once......what a flop. Rochester was a little better but a hack job was in order for a fit.

 

[FJ40Jim]

So have you ever done a real world Bionic carb and was it really worth junking out another carb for the venturis?

The extra CFM is only useful if the airpump underneath the carb needs the additional airflow.

Maybe it would be good if the engine was bored to 265CID and had cam, headers and bench validated portwork. Otherwise it is unnecessary. The USA carb is plenty big, it just needs tweaked to run good.

 

[FJ40Jim]

so if the Weber is "weaker/lame-er" how could your gas mileage decrease when using one. Are they less efficient? or is it just a figment of the imagination.

The weber 32/36 is a progressive 2bbl, like a 70-74 F carb. But it is a very small carb for a 4.2L engine. It will not run the engine on the economical primary, so it is usually into the richer secondary. And even that is not really enough for street driving loads, so then the power valve opens, adding more enrichment...

38 is different. It's a synchronous carb, like a holley or rochester, both bbls open simultaneously. To avoid overcarbureting the slow revving Cruiser engine w/ sudden throttle opening, the venturis are made very small and the jets are fat. This limits total airflow at WOT, but ensures a strong vacuum signal and reliable fuel flow. There is also the power circuit to contend with. Because the carb is small, it is frequently operated at high throttle openings which engages the power circuit, thereby further enriching the mixture.

There is one other issue w/ the typical Weber install, the throttle linkage rate is very different from a stock install. They end up w/ much less pedal travel. to the ignorant operator, it seems like the car is faster now because just breathing on the pedal makes the engine pull hard. So the driver enjoys/uses this newfound "power" because it seems so easy to access. The same power could be found on a stock vehicle by shortening the lever arm of the gas pedal.

 

[SDFJ60JFK]

Again excellent info Thanks Jim.

John
Lead ,SD

 

[grant5127]

I had a model # 2100 on my 40 once......what a flop.

No wonder.... that carb is from the 50s.... used on 100hp or less......

 

[cruiser88]

No wonder.... that carb is from the 50s.... used on 100hp or less......

holley 2100...naa it was like weber...to much fuel not worth a dam on steep inclines