Are there any problems with a variable venturi carburetor?
Thread Starter
|
Junior User
Joined: Apr 2003
Posts: 55
Likes: 0
Are there any problems with a variable venturi carburetor?
I'd never heard of a variable venturi carburetor before but found a site referring to them, what are their problems, how well do they work when properly set, and do they need a computer box to work correctly? I understand they might give better gas mileage, is this true? Would one work on my 400 with the stock manifold?
Moderator
Joined: Dec 2001
Posts: 22,436
Likes: 17
From: Louisville,Ky.
Are there any problems with a variable venturi carburetor?
They are crap, almost all of them were replaced with regular carbs. They had a TPS sensor and an ICM so they were connected to the ECM. I would highly recommend staying away from them. It was Fords first attempt at a fuel injection crossbreed.
Jimmy
Jimmy
Posting Guru
Joined: Aug 2000
Posts: 1,127
Likes: 3
From: (near) Denver USA
Are there any problems with a variable venturi carburetor?
Not all of the variable-venturi carbs had TPS and mixture control. They were used on 351W police cars with the DS2 ignition system (no ECM) for several years.
The VV carbs were introduced at about the same time as CFI (Ford's brand of throttle body fuel injection). If anything, the carbs with TPS and mixture control were a last stab at avoiding fuel injection with a closed-loop ECM.
I agree that you should avoid them if you can. The reason is that they are overly complicated for what they do (harder to work on), and they have little or no performance enhancement potential. They are nowhere near as "tunable" as the 2150 2V.
The VV carbs were introduced at about the same time as CFI (Ford's brand of throttle body fuel injection). If anything, the carbs with TPS and mixture control were a last stab at avoiding fuel injection with a closed-loop ECM.
I agree that you should avoid them if you can. The reason is that they are overly complicated for what they do (harder to work on), and they have little or no performance enhancement potential. They are nowhere near as "tunable" as the 2150 2V.
Moderator
Joined: Dec 2001
Posts: 22,436
Likes: 17
From: Louisville,Ky.
Are there any problems with a variable venturi carburetor?
Yeah, I used to have a 80 Crown Vic with the 351 VV and finally converted it to the Holley replacement. It ran sweet after that. It would probably be jetted to lean for a 400 anyway.
Elder User
Joined: Aug 2002
Posts: 535
Likes: 0
From: Laveen
Are there any problems with a variable venturi carburetor?
Variable venturis are a good idea and not a new one, the ford VV's were just a pain to work on. SU's have been around for years and aren't really too bad you had to keep oil in the tanks on top of the carbs as that was how the maintained the seal in the pistons witout precision machining. You would know when they were out of oil as your Volvo, MG, or whatever it was would start ******* out on you because the air would leak around the dry piston and the venturi wouldn't open.
The mikunis and other motorcycle carbs are variable venturi also but they depend on very close tolerance machining instead of oil and are popular on four bangers.
You can also get a Predator carb, it looks like a big cube it is variable venturi also but the venturis are operated by the throttle linkage if I remember right instead of vacumm. and I think it comes in a big 950 cfm two barrel, but with variable venturis you don't need four barrels
The mikunis and other motorcycle carbs are variable venturi also but they depend on very close tolerance machining instead of oil and are popular on four bangers.
You can also get a Predator carb, it looks like a big cube it is variable venturi also but the venturis are operated by the throttle linkage if I remember right instead of vacumm. and I think it comes in a big 950 cfm two barrel, but with variable venturis you don't need four barrels
Cargo Master
Joined: Jul 2000
Posts: 2,281
Likes: 18
From: Northern California
Are there any problems with a variable venturi carburetor?
The Predator carb does work on vac just like the SU's do but it's based on a spring control at the top of the carb. You simply adjust the spring for different resistance. They are a square 1 barrel design and flow up to about 960.
They use a replaceable cam for fuel control and are about as simple as they get.
The real downside is that they don't get good mpg, most that have tried them get 2~4mpg more from a holley. They do however offer excellent low/mid range torque and still great top end power.
I've been running mine for about 2 years and it's very tuneable and responsive, but the mpg hit does suck.
I used to work in a carb shop back when the ford vv started coming in and yes they are poor carbs. Good theory, poor design.
They use a replaceable cam for fuel control and are about as simple as they get.
The real downside is that they don't get good mpg, most that have tried them get 2~4mpg more from a holley. They do however offer excellent low/mid range torque and still great top end power.
I've been running mine for about 2 years and it's very tuneable and responsive, but the mpg hit does suck.
I used to work in a carb shop back when the ford vv started coming in and yes they are poor carbs. Good theory, poor design.
Elder User
Joined: Aug 2002
Posts: 535
Likes: 0
From: Laveen
Are there any problems with a variable venturi carburetor?
I had read somewhere that the predators were really only good for broadband power not economy, all of my experience with variable venturis was with SU's and motorcycles. I was happy with my volvo in Germany but I kept a can of Three in One in the trunk just for the carbs.
Trending Topics
New User
Joined: Dec 2010
Posts: 3
Likes: 0
Variable Venturi carburetors
Not all of the variable-venturi carbs had TPS and mixture control. They were used on 351W police cars with the DS2 ignition system (no ECM) for several years.
The VV carbs were introduced at about the same time as CFI (Ford's brand of throttle body fuel injection). If anything, the carbs with TPS and mixture control were a last stab at avoiding fuel injection with a closed-loop ECM.
I agree that you should avoid them if you can. The reason is that they are overly complicated for what they do (harder to work on), and they have little or no performance enhancement potential. They are nowhere near as "tunable" as the 2150 2V.
The VV carbs were introduced at about the same time as CFI (Ford's brand of throttle body fuel injection). If anything, the carbs with TPS and mixture control were a last stab at avoiding fuel injection with a closed-loop ECM.
I agree that you should avoid them if you can. The reason is that they are overly complicated for what they do (harder to work on), and they have little or no performance enhancement potential. They are nowhere near as "tunable" as the 2150 2V.
FTE Stories
Ford Trucks for Ford Truck Enthusiasts
10 Best Ford Truck Engines We Miss the Most!
Joe Kucinski
2026 Shelby F-150 Off-Road: Better Than a Raptor R?
Brett Foote
2027 Super Duty Carhartt Package First Look: 12 Things You NEED to Know!
Michael S. Palmer
10 Most Surprising 2026 Ford Truck Features!
Joe Kucinski
Top 10 Ford Trucks Coming to Mecum Indy 2026
Brett Foote
5 Best / 5 Worst Ford Truck Wheels of All Time
Joe Kucinski
Ford Super Duty: 5 Things Owners LOVE, 5 Things They LOATHE!
Joe Kucinski
Every 2026 Ford Truck Engine RANKED from WORST to FIRST!
Michael S. Palmer
The Best F-150 Deal of Every Trim Level (XL through Raptor)
Joe Kucinski
New User
Joined: Dec 2010
Posts: 3
Likes: 0
VV carbs
The Predator carb does work on vac just like the SU's do but it's based on a spring control at the top of the carb. You simply adjust the spring for different resistance. They are a square 1 barrel design and flow up to about 960.
They use a replaceable cam for fuel control and are about as simple as they get.
The real downside is that they don't get good mpg, most that have tried them get 2~4mpg more from a holley. They do however offer excellent low/mid range torque and still great top end power.
I've been running mine for about 2 years and it's very tuneable and responsive, but the mpg hit does suck.
I used to work in a carb shop back when the ford vv started coming in and yes they are poor carbs. Good theory, poor design.
They use a replaceable cam for fuel control and are about as simple as they get.
The real downside is that they don't get good mpg, most that have tried them get 2~4mpg more from a holley. They do however offer excellent low/mid range torque and still great top end power.
I've been running mine for about 2 years and it's very tuneable and responsive, but the mpg hit does suck.
I used to work in a carb shop back when the ford vv started coming in and yes they are poor carbs. Good theory, poor design.
1st Gear
Joined: Aug 2022
Posts: 1
Likes: 0
Me 2, I had an 85 Crown Victoria police car great car sucky carb. It would not idle, sometimes it would sometimes I would just die going down the road it would look like an old F4 jet at times too with all the black smoke. Once I replacedv he junk vv carb with a Holley it ran sweet like a different car!
Thread
Thread Starter
Forum
Replies
Last Post
CustomCab59
1980 - 1986 Bullnose F100, F150 & Larger F-Series Trucks
59
Nov 7, 2020 02:52 PM
PeeWee525
1980 - 1986 Bullnose F100, F150 & Larger F-Series Trucks
9
May 26, 2017 12:32 PM
351 power
Fuel Injection, Carburetion & Fuel System
4
Oct 17, 2003 09:13 PM
HerculesEngine
Small Block V8 (221, 260, 289, 5.0/302, 5.8/351W)
3
Apr 6, 2002 06:48 PM
Bull
Small Block V8 (221, 260, 289, 5.0/302, 5.8/351W)
17
Jan 31, 2002 09:38 PM
2150, 351w, carb, carburator, carburetor, carburetors, ford, holley, maintenance, piston, replacement, specs, variable, venturi, vv
