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NJ John
Samba Member
Joined: September 21, 2007
Posts: 3018
Location: HdG, MD & NJ
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 Posted: Wed Aug 20, 2025 12:54 pm Post subject: Mixed size venturis |
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Is there ever a situation where you would have on smaller venturi? I had a set of drla’s and it had one smaller vent. I’m not sure if it was positioned on #3 cylinder. These carbs been sitting and I’m thinking of using them, again. They were bought used and where once on a race dirt buggy. I used them about 30 years ago and never noticed the venturi.
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1973 standard, yellow, lowered, 3” narrowed front, 1600 blo-thru turbo w/single dell 15.4@86, so far
11.41 et buggy. Long gone
Let’s go O’s! Let’s go O’s!
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67rustavenger
Samba Member
Joined: February 24, 2015
Posts: 11505
Location: Oregon
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| Posted: Wed Aug 20, 2025 3:42 pm Post subject: Re: Mixed size venturis |
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| NJ John wrote: |
| Is there ever a situation where you would have on smaller venturi? I had a set of drla’s and it had one smaller vent. I’m not sure if it was positioned on #3 cylinder. These carbs been sitting and I’m thinking of using them, again. They were bought used and where once on a race dirt buggy. I used them about 30 years ago and never noticed the venturi. |
I've seen it on a single side draft Dellorto carb, along with staggered jetting.
Never seen one smaller vent of the four on a set of DRLA's.
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I have learned over the years.
Cheap parts are gonna disappoint you.
Buy Once, Cry Once!
There's never enough time to do it right the first time. But there's always enough time to do it thrice.
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2003 Astrovan? GFYS again, Xevin! 
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BFB
Samba Member
Joined: November 03, 2014
Posts: 3074
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| Posted: Wed Aug 20, 2025 3:46 pm Post subject: Re: Mixed size venturis |
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If it’s used a single center mount and on an open intake… ( theres a name for it and my dumbass brain cant think of it ).
I have a 45 DCEO with different sized chokes, venturis, jets, and velocity stacks too. It’s on a draw-through turbo setup.
Set up like this you can stagger when the mains come in, tuning one throat for lower rpm and the other higher.
Dont see how itd do anything but cause problems run as duals though. Maybe someone put it in and didnt realize it?
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NJ John
Samba Member
Joined: September 21, 2007
Posts: 3018
Location: HdG, MD & NJ
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| Posted: Wed Aug 20, 2025 4:21 pm Post subject: Re: Mixed size venturis |
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I’m kinda thinking it was just done by mistake.
_________________
1973 standard, yellow, lowered, 3” narrowed front, 1600 blo-thru turbo w/single dell 15.4@86, so far
11.41 et buggy. Long gone
Let’s go O’s! Let’s go O’s!
https://www.youtube.com/@AirSpooledGarage |
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67rustavenger
Samba Member
Joined: February 24, 2015
Posts: 11505
Location: Oregon
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| Posted: Wed Aug 20, 2025 4:39 pm Post subject: Re: Mixed size venturis |
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| BFB wrote: |
If it’s used a single center mount and on an open intake… ( theres a name for it and my dumbass brain cant think of it ).
I have a 45 DCEO with different sized chokes, venturis, jets, and velocity stacks too. It’s on a draw-through turbo setup.
Set up like this you can stagger when the mains come in, tuning one throat for lower rpm and the other higher.
Dont see how itd do anything but cause problems run as duals though. Maybe someone put it in and didnt realize it? |
Yup, that was the setup I saw/worked on last September. It just had staggered jetting not the vents and velocity stacks.
Of course after we rejetted the carb. The owner turnt up the boost to max and fried a piston and head in short order.
_________________
I have learned over the years.
Cheap parts are gonna disappoint you.
Buy Once, Cry Once!
There's never enough time to do it right the first time. But there's always enough time to do it thrice.
GFY's Xevin and VW_Jimbo!
2003 Astrovan? GFYS again, Xevin!
Don't let your bad ideas remain, ideas! |
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modok
Samba Member
Joined: October 30, 2009
Posts: 27750
Location: Colorado Springs
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| Posted: Wed Aug 20, 2025 5:14 pm Post subject: Re: Mixed size venturis |
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Probably a mistake, BUT
it's ok if the main jet matches
4.1 times vent size
based on the REAL size, not the imaginary size
Vents ARE jets, and just like all jets, it's best to measure them instead of ONLY going by the size marked on it. |
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BFB
Samba Member
Joined: November 03, 2014
Posts: 3074
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| Posted: Wed Aug 20, 2025 8:01 pm Post subject: Re: Mixed size venturis |
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| 67rustavenger wrote: |
| BFB wrote: |
If it’s used a single center mount and on an open intake… ( theres a name for it and my dumbass brain cant think of it ).
I have a 45 DCEO with different sized chokes, venturis, jets, and velocity stacks too. It’s on a draw-through turbo setup.
Set up like this you can stagger when the mains come in, tuning one throat for lower rpm and the other higher.
Dont see how itd do anything but cause problems run as duals though. Maybe someone put it in and didnt realize it? |
Yup, that was the setup I saw/worked on last September. It just had staggered jetting not the vents and velocity stacks.
Of course after we rejetted the carb. The owner turnt up the boost to max and fried a piston and head in short order.
One thing ive learned, you cant really complain about customers that do dumb stuff and are willing to pay for their mistakes to be fixed.
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_________________
"how am i supposed to torque the rear wheel nut to 250 ft lbs??? " - clonebug
An interesting thing happens in forums where everyone starts parroting the same thing and "common knowledge" takes over.
Most experts aren't. |
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