2-Barrel vs. 4-Barrel Carb
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Cargo Master
Joined: Dec 2004
Posts: 3,362
Likes: 22
From: Florence, SC
2-Barrel vs. 4-Barrel Carb
My old Motorcraft carburetor for my 302 is on its last leg and needs to be rebuilt or replaced. What, if any, advantage does a 2-Barrel carb have over a 4-Barrel? I am asking this question because whenever I talk to mechanics around my area, they seem to try to get me to stay with a 2-Barrel. I mean, from my understanding, the only major work to do is change the intake and get a 4-Barrel carb to replace my 2-Barrel, right?
Lead Driver
Joined: Dec 2002
Posts: 5,489
Likes: 13
From: Kuna ID
You can get better fuel economy with a 4bbl. A 2bbl carb just has 2 large holes to feed. A 4bbl carb has 4 smaller holes. If you can keep your foot out of the pedal, you are essentially only useing the 2 smaller holes on the front of the carb.
New User
Joined: Jan 2008
Posts: 0
Likes: 24
The 2v will provide more Torque at low Rpm. (better for yanking the truck out of a hole)
The 4v will provide more HP at high Rpm.
There is square bore and spread bore carbs intakes.
The square bore is like this
oo
oo
The spread bore is like this
oo
OO
The CFM rate on a 2v is usually around 480 -530 cfm
The CFM Rate on a 4v is usually 650 to 750 with the secondaries activated.
FTE has a Fuel Delivery forum for specific topics like this.
The 4v will provide more HP at high Rpm.
There is square bore and spread bore carbs intakes.
The square bore is like this
oo
oo
The spread bore is like this
oo
OO
The CFM rate on a 2v is usually around 480 -530 cfm
The CFM Rate on a 4v is usually 650 to 750 with the secondaries activated.
FTE has a Fuel Delivery forum for specific topics like this.
Last edited by Mil1ion; Oct 12, 2006 at 05:21 PM.
Postmaster
Joined: Dec 2004
Posts: 2,941
Likes: 30
From: Maple Valley, WA
Originally Posted by Mil1ion
The 2v will provide more Torque at low Rpm. (better for yanking the truck out of a hole)
The 4v will provide more HP at high Rpm.
There is square bore and spread bore carbs intakes.
The square bore is like this
oo
oo
The spread bore is like this
oo
OO
The CFM rate on a 2v is usually around 480 -530 cfm
The CFM Rate on a 4v is usually 650 to 750 with the secondaries activated.
FTE has a Fuel Delivery forum for specific topics like this.
The 4v will provide more HP at high Rpm.
There is square bore and spread bore carbs intakes.
The square bore is like this
oo
oo
The spread bore is like this
oo
OO
The CFM rate on a 2v is usually around 480 -530 cfm
The CFM Rate on a 4v is usually 650 to 750 with the secondaries activated.
FTE has a Fuel Delivery forum for specific topics like this.
Senior User
Joined: Jun 2004
Posts: 282
Likes: 0
From: Winchester
I put one on my 83 F-100 with a stock 302.If I had it to do again I would just have rebuilt the 2 barrel.I had to come up with some linkage for the aod.I really didn,t think it was worth the hassel when I got it on,but I use it as just a truck not a hot rod.I very seldom got on it.
Super Moderator
Joined: Apr 2004
Posts: 34,466
Likes: 2,798
Rebuild the 2bbl for under $50 including beer or diet coke during the job.
You can get better mpg with a 4bbl but you won't.
If you go with a small (390 cfm) 4bbl, maybe you'll get better mpg.
If you research 4bbl manifolds, and go with a 600 cfm 4bbl, you can really wake up your motor, but it will cost you.
You can get better mpg with a 4bbl but you won't.
If you go with a small (390 cfm) 4bbl, maybe you'll get better mpg.
If you research 4bbl manifolds, and go with a 600 cfm 4bbl, you can really wake up your motor, but it will cost you.
New User
Joined: Jan 2008
Posts: 0
Likes: 24
Originally Posted by RacinNdrummin
A 2bbl Wont give you more torque, Proper Carb sizing will. 2bbls are easier to manufacture, thats why they came stock. You will get more Torque and HP as well as fuel mileage with a Vacuum Secondary 4bbl carb set up, they were designed for that purpose.
Please Re-read the 1st two sentences.,
The Larger holes and fuel delivery on a 2 bbl carb will deliver more fuel to the engine than the 2 mains of a 4 bbl carb thus delvering more Torque.
This is one reason they put 2 bbl carbs on most trucks, More Low RPM Torque from idle to top of power band.
Vacuum secondaries don't come on until almost full throttle.
Last edited by Mil1ion; Oct 14, 2006 at 01:56 AM.
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Cargo Master
Joined: Dec 2004
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From: Florence, SC
Thanks guys! This is exactly what I was looking for. Basically I was wondering, why, if the 4-barrel is so much better than the two barrel, did so many Ford trucks come equipped with a 2 barrel carburetor. I knew there had to be a good enough reason why the engineers did it this way.
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Senior User
Joined: Apr 2006
Posts: 105
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From: gloucester va
I dont know, I put a 600 cfm edelbrock on my 351w and the truck is running alot smoother and I havent driven the truck to work lately(60 miles one way) to check gas mileage but local running around is hovering around 11.5 - 12mpg
Moderator
Joined: Jan 2001
Posts: 56,946
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From: Virginia
Most people get a boost in performance from a 4bbl over the stock 2bbl because the 4bbl is usually a "universal fit" and is jetted richer than the stock 2bbl.
In the original engine set-up, there is a lot of emissions stuff, and the engine has a delicate balance of tuning with timing, and jetting of the original carb along with the egr and other components. Disconnect one thing, or change one thing,(even the exhaust system) and you mess up the tune of the engine. And the engineers did have their hands tied a little bit too, since they have government emissions standards to keep.
Buy a aftermarket 4bbl(or even an aftermarket 2bbl) and it will be jetted a little on the rich side, which will cover up the many sins from taking emission devices off, putting headers on, advancing the timing, etc. So it will naturally tend to run better in these situations.
In the original engine set-up, there is a lot of emissions stuff, and the engine has a delicate balance of tuning with timing, and jetting of the original carb along with the egr and other components. Disconnect one thing, or change one thing,(even the exhaust system) and you mess up the tune of the engine. And the engineers did have their hands tied a little bit too, since they have government emissions standards to keep.
Buy a aftermarket 4bbl(or even an aftermarket 2bbl) and it will be jetted a little on the rich side, which will cover up the many sins from taking emission devices off, putting headers on, advancing the timing, etc. So it will naturally tend to run better in these situations.
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