2008 Toyota Avalon Carburetor Air and Fuel Delivery - Demon Fuel Systems, Edelbrock, Holley, Jet Performance, Mr Gasket, NOS, Proform, Quick Fuel Technology

Carburetor Quick Fuel Technology

Part # P311-56B6069 Manu # 7-28QFT Condition: New

Qty:

In Stock & Ready to Ship

Best Price: $38.38

Screw In Emulsion Restriction
Screw In Emulsion Restriction; 6-32 Thread; 0.028 Size; 4 pc.;
Product Attributes:
- Jet Size: 0.028
- WARNING CA Proposition 65: Yes
- WARNING CA Proposition 65 Message: Warning: Cancer And Reproductive Harm - Www.p65warnings.ca.gov
Features:
- Stamped For Identification
- 1 Each
6-32 Screw-in Restriction .028 in. - Includes (4) restrictions

Fitment Warning:
This is a Universal/Non Application Specific Product. To install this part, you made need to cut, weld, or make other modifications to your vehicle.

Brand: Quick Fuel Technology

Vehicle

Carburetor Quick Fuel Technology

Part # P311-0C1CDD0 Manu # SS-780-VS Condition: New

Qty:

In Stock & Ready to Ship

Best Price: $906.24

SS Series Carburetor
SS Series Carburetor; 780 cfm ; 1 11/16 in. Bore;
Product Attributes:
- Barrel: Four
- Billet Color: Red
- Booster Type: Down Leg
- Carburetor Type: Super Street Series
- CFM: 780
- Choke: Electric
- Circuit: 2
- Emission: Without Egr
- Flange: Square Bore
- Fuel System Type: Carbureted
- Fuel Type: Gasoline
- High Speed Air Bleed: 33
- Idle Air Bleed Size: 70
- Primary Main Jet: 74
- Primary Power Valve: 65
- Primary Pump Nozzle Size: 33
- Secondary Main Jet: 82
- Secondary Type: Vacuum
- Supercharged Application: No
- Throttle Bore: 1.6875 In.
- Usage: Street
- WARNING CA Proposition 65: Yes
- WARNING CA Proposition 65 Message: Warning: Cancer And Reproductive Harm - Www.p65warnings.ca.gov
Features:
- 1 11/16 in. Throttle Bore Size
- 22-74 Primary Jet
- 22-82 Secondary Jet
- 26-70 Idle Bleed
- 26-33 Hi Speed Bleed
- 25-65 Power Valve
- 18-2 Needle And Seat
- Gas Fuel
Super Street Series carburetors combine street-friendly drivability and track-capable performance in a single value-oriented package. Setting them apart from ordinary street carbs, they feature billet dual metering blocks and throttle-bodies that offer tighter tolerances and eliminate porosity. Not only are Super Street Series carbs available with both vacuum or mechanical secondaries, QFT also offers models designed and calibrated specifically for E85 fuel and blow-through forced induction applications. Running alternative fuel or boost no longer requires an expensive custom carburetor. All SS-Series carburetors are equipped with universal throttle levers to accommodate Ford A/T kickdown, GM 700 R4 mounting holes, and ability to mount brackets for Chrysler vehicles. Available in 8 different sizes, bolting on the ultimate street/strip carburetor has never been easier. Billet dual metering blocks & throttle bodies for improved durability Changeable idle, high-speed air bleeds & power valve restrictions Dual inlet fuel bowls with dual sight glass windows for easy float adjustment4-Corner idle for precise idle and smooth transition Quickset vacuum secondary housing fully adjustable opening rate by turning a screw - no more spring assortments or torn diaphragms. Fully-adjustable electric choke with easy one wire hookup Race-ready with notched secondary floats and jet extensions Polished or Black Diamond finish available (some models)

Fitment Warning:
This is a Universal/Non Application Specific Product. To install this part, you made need to cut, weld, or make other modifications to your vehicle.

Brand: Quick Fuel Technology

Vehicle

Carburetor Quick Fuel Technology

Part # P311-05F8FA0 Manu # BR-67211 Condition: New

Qty:

In Stock & Ready to Ship

Best Price: $654.56

Brawler® Street Carburetor
Brawler® Street Carburetor; 4 bbl; 600 CFM; Mechanical Secondary; Electric Choke; Dual Fuel Inlet; Carb Fuel System; Gas; Down Leg Booster; 1-9/16 in. Throttle Bore; Off-Road Use;
Product Attributes:
- Barrel: Four
- Billet Color: Black
- Booster Type: Down Leg
- CFM: 600
- Choke: Electric
- Circuit: 2
- Emission: With Egr
- Flange: Square Bore
- Fuel Inlet: Dual
- Fuel System Type: Carbureted
- Fuel Type: Gasoline
- High Speed Air Bleed: 28
- Idle Air Bleed Size: 70
- Primary Main Jet: 66
- Primary Power Valve: 6.5
- Primary Pump Nozzle Size: 31
- Secondary Main Jet: 72
- Secondary Type: Mechanical
- Supercharged Application: No
- Throttle Bore: 1.5625 In.
- Usage: Street
- WARNING CA Proposition 65: Yes
- WARNING CA Proposition 65 Message: Warning: Cancer And Reproductive Harm - Www.p65warnings.ca.gov
Features:
- 600 CFM
- Mechanical Secondary
Q-Series - The Q-Series is our most comprehensive line of drag race carburetors, and is a popular choice due to its blend of performance and drivability. They are available for use with gasoline, methanol, and E85 fuels, and come in both mechanical and vacuum secondary models. All single 4-BBL. applications come with notched floats and secondary jet extensions which help solve any lean condition you may have on hard acceleration. The Q-Series, has all the tuning features you would expect from a carburetor that's ready to race.

Fitment Warning:
This is a Universal/Non Application Specific Product. To install this part, you made need to cut, weld, or make other modifications to your vehicle.

Brand: Quick Fuel Technology

Vehicle

Carburetor Quick Fuel Technology

Part # P311-2D2D0C7 Manu # SL-450-VSTRR Condition: New

Qty:

In Stock & Ready to Ship

Best Price: $513.03

Slayer Series Carburetor
Slayer Series Carburetor; 450 cfm.; Vacuum Secondary; Electric Choke; Rear; Pairs w/PN[SL-450-VSTRF] For Tunnel Ram Application; Cast Aluminum; Polished;
Product Attributes:
- Barrel: Four
- Billet Color: Diecast-no Billet
- Booster Type: Straight
- Carburetor Type: Slayer Series
- CFM: 450
- Choke: Electric
- Circuit: 2
- Emission: Without Egr
- Flange: Square Bore
- Fuel System Type: Carbureted
- Fuel Type: Gasoline
- High Speed Air Bleed: 35;33
- Idle Air Bleed Size: 70;39
- Primary Main Jet: 56
- Primary Power Valve: 65
- Primary Pump Nozzle Size: 25
- Secondary Main Jet: 60
- Secondary Type: Vacuum
- Supercharged Application: No
- Throttle Bore: 1.5625 In.
- Usage: Street
- WARNING CA Proposition 65: Yes
- WARNING CA Proposition 65 Message: Warning: Cancer And Reproductive Harm - Www.p65warnings.ca.gov
Features:
- Matched For Tunnel Ram/Dual Carb Applications
- Electric Choke For Easier Cold Starts
- Calibrated For Crisp Response
- Purchase SL-450-VSTRR And SL-450-VSTRF Together
- Vacuum Secondary
- Single Metering Block/Secondary Metering Plate
- Single Sight Glass Window
- Changeable Air Bleeds
- Adjustable Needle And Seats
Combining the years of experience with tunnel ram and dual carburetor applications, Quick Fuel has developed a matched carburetor pair based on the 450 Slayer series for your tunnel ram application. The front carburetor is a no choke model calibrated to work with the rear carburetor for the performance that you are looking for. Purchase the SL-450-VSTRF (front) along with the SL-450-VSTRR (rear) for the matched performance for your dual carburetor application. Slayer Series street carburetors are designed with many of the same innovations and features that are built into all QFT race-winning carburetors, including changeable air bleeds and power valve channel restrictions. Its designed with a secondary metering plate with changeable jets, and features all aluminum components for additional weight savings. All Slayer Series carburetors are equipped with universal throttle levers to accommodate Ford A/T kickdown, GM 700 R4 mounting holes, and ability to mount brackets for Chrysler vehicles. Slayer Series are available in 450, 600, and 750 cfm vacuum secondary models. Vacuum Secondaries Electric Choke Single Metering Block Secondary Metering Plate Cast Aluminum Throttle Body Single Sight Glass Windows Changeable Air Bleeds Adjustable Needles & Seats

Fitment Warning:
This is a Universal/Non Application Specific Product. To install this part, you made need to cut, weld, or make other modifications to your vehicle.

Brand: Quick Fuel Technology

Vehicle

Carburetor Quick Fuel Technology

Part # P311-233B15A Manu # BR-67304 Condition: New

Qty:

In Stock & Ready to Ship

Best Price: $931.87

Brawler® Race Carburetor
Brawler® Race Carburetor; 4 bbl; 950 CFM; Mechanical Secondary; Dual Fuel Inlet; Carb Fuel System; Gas; Down Leg Booster; 1-3/4 in. Throttle Bore; Off-Road Use;
Product Attributes:
- Barrel: Four
- Billet Color: Purple
- Booster Type: Down Leg
- CFM: 950
- Choke: None
- Circuit: 2
- Emission: Without Egr
- Flange: Square Bore
- Fuel Inlet: Dual
- Fuel System Type: Carbureted
- Fuel Type: Gasoline
- High Speed Air Bleed: 32
- Idle Air Bleed Size: 73
- Primary Main Jet: 78
- Primary Power Valve: 4.5
- Primary Pump Nozzle Size: 33
- Secondary Main Jet: 86
- Secondary Type: Mechanical
- Supercharged Application: No
- Throttle Bore: 1.750 In.
- Usage: Racing/circle Track
- WARNING CA Proposition 65: Yes
- WARNING CA Proposition 65 Message: Warning: Cancer And Reproductive Harm - Www.p65warnings.ca.gov
Features:
- The Latest In Technology In Air/Fuel Calibrations
- For Street Or Race Engine Demands
- Available In Both Vacuum/Mechanical Secondary Versions
- All Models Have Dual Inlet Fuel Bowls
- With Sight Glass Windows For Safe/Easy Float Adjustments
- Changeable Idle/High Speed Air Bleeds For Easy Tuning
- Four-Corner Idle Adjustment on Mechanical Secondary Models
- Performance Models Includes Billet Metering Blocks/Throttle Bodies
- With Precision Throttle Shafts To Ensure Long Term Performance
- Black Coated Finish w/Purple Billet Metering Blocks/Throttle Body
Quick Fuel Technology continues to lead the pack with their newest family of carburetors named Brawler. Brawler carburetors are precision machined and hand-assembled by craftsman right here in the USA. The Brawler family of carburetors include models for your daily driver to your race car. These carburetors work hard just as their name implies- just raw bare knuckled performance that you can rely on. Don't let the budget-friendly price fool you, the Brawler development focused on the performance you want and not the pretty box that it comes in. Brawlers come with the latest technology in air/fuel calibrations for today's street or race engine demands. The Brawler family of carburetors are all made from light-weight aluminum components and are available in both vacuum and mechanical secondary models. They offer all the tunability that you would find from more expensive carburetors in the market, including four-corner idle adjustment on all models.

Fitment Warning:
This is a Universal/Non Application Specific Product. To install this part, you made need to cut, weld, or make other modifications to your vehicle.

Brand: Quick Fuel Technology

Vehicle

Carburetor Quick Fuel Technology

Part # P311-08EECA6 Manu # M-750 Condition: New

Qty:

In Stock & Ready to Ship

Best Price: $958.17

Marine Series Carburetor
Marine Series Carburetor; 750 cfm.; Mechanical Secondary; Electric Choke; Black Diamond Finish;
Product Attributes:
- Barrel: Four
- Billet Color: Diecast-no Billet
- Booster Type: Down Leg
- Carburetor Type: Marine
- CFM: 750
- Choke: Electric
- Circuit: 2
- Emission: Without Egr
- Flange: Oem
- Fuel System Type: Carbureted
- Fuel Type: Gasoline
- High Speed Air Bleed: 31
- Idle Air Bleed Size: 70
- Marine Engine Size: Universal
- Primary Main Jet: 75
- Primary Power Valve: 65
- Primary Pump Nozzle Size: 33
- Secondary Main Jet: 83
- Secondary Type: Mechanical
- Supercharged Application: No
- Throttle Bore: 1.6875 In.
- Usage: Marine
- WARNING CA Proposition 65: Yes
- WARNING CA Proposition 65 Message: Warning: Cancer And Reproductive Harm - Www.p65warnings.ca.gov
Features:
- Exclusive Black Diamond Coating For Enhanced Corrosion Protection
- Coating Provides a 6% Reduction In Fuel Temperature
- Electric Choke - Fully Adjustable One Wire Hookup
- J Tubes To Prevent Spillage
- PTFE-Coated Throttle Shafts w/PTFE Bearing Ribbons
- Built In Sight Glass Windows For Easy Float Adjustment
- Changeable Primary Idle Feed And Power Valve Channel Restrictions
- Changeable Idle Air And High Speed Bleeds
- QuickLink Secondary Adj. For Fast/Easy Changing Of Opening Rates
QFT brings its engineering expertise to the marine market. The M-Series feature billet-style metering blocks and throttle bodies for more precise performance and exceptional strength. Exclusive Black Diamond coating for enhanced corrosion protection and appearance, coating provides a 6% reduction in fuel temperature Electric choke - Fully adjustable, one wire hookupJ tubes to prevent spillagePTFE-coated throttle shafts with PTFE bearing ribbons and stainless steel plates Built-in sight glass windows for easy float adjustment Changeable primary idle feed and power valve channel restrictions, plus changeable idle air and high speed bleeds QuickLink secondary adjustment for fast and easy changing of opening rates Available in eight different sizes from 350-1,050 cfm

Fitment Warning:
This is a Universal/Non Application Specific Product. To install this part, you made need to cut, weld, or make other modifications to your vehicle.

Brand: Quick Fuel Technology

Vehicle

Carburetor Quick Fuel Technology

Part # P311-4F1DC29 Manu # FX-4711 Condition: New

Qty:

In Stock & Ready to Ship

Best Price: $1,750.65

QFX Series Carburetor
QFX Series Carburetor; 1150 cfm.; 1.800 in. Venturi; Dominator; All Aluminum Construction; Polished Finish w/Red Anodized Billet Metering Blocks;
Product Attributes:
- Barrel: Four
- Billet Color: Red
- Booster Type: Annular
- Carburetor Type: Fx Series
- CFM: 1150
- Choke: None
- Circuit: 3
- Emission: Without Egr
- Flange: Oem
- Fuel System Type: Carbureted
- Fuel Type: Gasoline
- High Speed Air Bleed: 36
- Idle Air Bleed Size: 47
- Intermediate Air Bleed: 85
- Primary Main Jet: 94
- Primary Power Valve: N/a
- Primary Pump Nozzle Size: 37
- Secondary Main Jet: 94
- Secondary Type: Mechanical
- Supercharged Application: No
- Throttle Bore: 2.000 In.
- Usage: Racing
- WARNING CA Proposition 65: Yes
- WARNING CA Proposition 65 Message: Warning: Cancer And Reproductive Harm - Www.p65warnings.ca.gov
Features:
- QFX Aluminum Main Body w/Raised Venturi
- Billet Aluminum Metering Blocks w/Screw In Restrictions
- Aluminum Fuel Bowls w/Dual Sight Windows/Fuel Inlets
- Nitrophyl Floats and Jet Extensions
- Viton 0.130 in. Needles and Seats
- Billet Aluminum Annular Booster Inserts
- QuickLink Adjustable Secondary Opening Adjustment
- Hand Assembled and Engine Tested
Serious drag racing demand a serious drag racing carburetor, and the QFX-Series stands as the flagship model in QFTs lineup. Raised air horns improve entry angle into the venturi while ensuring undisrupted flow over the air bleeds. Annular boosters with CNC-machined billet aluminum inserts provide increased air flow, a stronger signal, and less turbulence. QFX carbs offer unparalleled fuel atomization with annular boosters specific for either gas, methanol, or E85 fuels. Five-emulsion billet metering blocks and four-corner idle circuits offer flexible tunability that todays high-horsepower engines demand. To cover a broad range of applications, methanol- and E85-compatible models, as well as two- and three-circuit fuel systems, are available. Ready to run out of the box, the QFX-Series carburetor will help you get to the winners circle.QFX aluminum main body w/raised venturi Billet aluminum metering blocks with screw in restrictions Aluminum fuel bowls with dual sight windows and fuel inletsNitrophyl(R) Floats (notched rear) and jet extensions Viton .130 in. Needles and Seats Billet Aluminum annular booster inserts QuickLink„¢ adjustable secondary opening adjustment Hand assembled and engine tested

Fitment Warning:
This is a Universal/Non Application Specific Product. To install this part, you made need to cut, weld, or make other modifications to your vehicle.

Brand: Quick Fuel Technology

Vehicle

Carburetor Quick Fuel Technology

Part # P311-1FC2748 Manu # SL-600-VS Condition: New

Qty:

In Stock & Ready to Ship

Best Price: $508.60

Slayer Series Carburetor
Slayer Series Carburetor; 600 cfm.; Vacuum Secondary; Electric Choke; All Aluminum Construction; Polished Finish;
Product Attributes:
- Barrel: Four
- Billet Color: Diecast-no Billet
- Booster Type: Straight
- Carburetor Type: Slayer Series
- CFM: 600
- Choke: Electric
- Circuit: 2
- Emission: Without Egr
- Flange: Oem
- Fuel System Type: Carbureted
- Fuel Type: Gasoline
- High Speed Air Bleed: 31
- Idle Air Bleed Size: 70;39
- Primary Main Jet: 68
- Primary Power Valve: 65
- Primary Pump Nozzle Size: 31
- Secondary Main Jet: 74
- Secondary Type: Vacuum
- Supercharged Application: No
- Throttle Bore: 1.5625 In.
- Usage: Street
- WARNING CA Proposition 65: Yes
- WARNING CA Proposition 65 Message: Warning: Cancer And Reproductive Harm - Www.p65warnings.ca.gov
Features:
- 1 9/16 in. Throttle Bore Size
- 22-68 Primary Jet
- 22-74 Secondary Jet
- 26-70/26-39 Idle Bleed
- 26-31 Hi Speed Bleed
- 21-31 Pump Nozzle
- 25-65 Power Valve
- 18-1 Needle And Seat
- Gas Fuel
Slayer Series street carburetors are designed with many of the same innovations and features that are built into all QFT race-winning carburetors, including changeable air bleeds and power valve channel restrictions. Its designed with a secondary metering plate with changeable jets, and features all aluminum components for additional weight savings. All Slayer Series carburetors are equipped with universal throttle levers to accommodate Ford A/T kickdown, GM 700 R4 mounting holes, and ability to mount brackets for Chrysler vehicles. Slayer Series are available in 450, 600, and 750 cfm vacuum secondary models. Vacuum Secondaries Electric Choke Single Metering Block Secondary Metering Plate Cast Aluminum Throttle Body Single Sight Glass Windows Changeable Air Bleeds Adjustable Needles & Seats Notched Secondary Floats w/Jet Extensions

Fitment Warning:
This is a Universal/Non Application Specific Product. To install this part, you made need to cut, weld, or make other modifications to your vehicle.

Brand: Quick Fuel Technology

Vehicle

Carburetor Quick Fuel Technology

Part # P311-1D0382E Manu # BR-67302 Condition: New

Qty:

In Stock & Ready to Ship

Best Price: $844.89

Brawler® Race Carburetor
Brawler® Race Carburetor; 4 bbl; 750 CFM; Mechanical Secondary; Dual Fuel Inlet; Carb Fuel System; Gas; Down Leg Booster; 1-11/16 in. Throttle Bore; Black Finish; Off-Road Use;
Product Attributes:
- Barrel: Four
- Billet Color: Purple
- Booster Type: Down Leg
- CFM: 750
- Choke: None
- Circuit: 2
- Emission: Without Egr
- Flange: Square Bore
- Fuel Inlet: Dual
- Fuel System Type: Carbureted
- Fuel Type: Gasoline
- High Speed Air Bleed: 33
- Idle Air Bleed Size: 73
- Primary Main Jet: 74
- Primary Power Valve: 4.5
- Primary Pump Nozzle Size: 31
- Secondary Main Jet: 84
- Secondary Type: Mechanical
- Supercharged Application: No
- Throttle Bore: 1.6875 In.
- Usage: Racing/circle Track
- WARNING CA Proposition 65: Yes
- WARNING CA Proposition 65 Message: Warning: Cancer And Reproductive Harm - Www.p65warnings.ca.gov
Features:
- The Latest In Technology In Air/Fuel Calibrations
- For Street Or Race Engine Demands
- Available In Both Vacuum/Mechanical Secondary Versions
- All Models Have Dual Inlet Fuel Bowls
- With Sight Glass Windows For Safe/Easy Float Adjustments
- Changeable Idle/High Speed Air Bleeds For Easy Tuning
- Four-Corner Idle Adjustment on Mechanical Secondary Models
- Performance Models Includes Billet Metering Blocks/Throttle Bodies
- With Precision Throttle Shafts To Ensure Long Term Performance
- Black Coated Finish w/Purple Billet Metering Blocks/Throttle Body
Quick Fuel Technology continues to lead the pack with their newest family of carburetors named Brawler. Brawler carburetors are precision machined and hand-assembled by craftsman right here in the USA. The Brawler family of carburetors include models for your daily driver to your race car. These carburetors work hard just as their name implies- just raw bare knuckled performance that you can rely on. Don't let the budget-friendly price fool you, the Brawler development focused on the performance you want and not the pretty box that it comes in. Brawlers come with the latest technology in air/fuel calibrations for today's street or race engine demands. The Brawler family of carburetors are all made from light-weight aluminum components and are available in both vacuum and mechanical secondary models. They offer all the tunability that you would find from more expensive carburetors in the market, including four-corner idle adjustment on all models.

Fitment Warning:
This is a Universal/Non Application Specific Product. To install this part, you made need to cut, weld, or make other modifications to your vehicle.

Brand: Quick Fuel Technology

Vehicle

Carburetor Quick Fuel Technology

Part # P311-2D2C123 Manu # SQ-750 Condition: New

Qty:

In Stock & Ready to Ship

Best Price: $790.93

Street Q Series Carburetor
Street Q Series Carburetor; 750 cfm.; Mechanical Secondary; Polished Finish;
Product Attributes:
- Barrel: Four
- Billet Color: Diecast-no Billet
- Booster Type: Down Leg
- Carburetor Type: Street-q Series
- CFM: 750
- Choke: None
- Circuit: 2
- Emission: Without Egr
- Flange: Oem
- Fuel System Type: Carbureted
- Fuel Type: Gasoline
- High Speed Air Bleed: 33
- Idle Air Bleed Size: 70
- Primary Main Jet: 74
- Primary Power Valve: 45
- Primary Pump Nozzle Size: 33
- Secondary Main Jet: 84
- Secondary Type: Mechanical
- Supercharged Application: No
- Throttle Bore: 1.6875 In.
- Usage: Street/strip
- WARNING CA Proposition 65: Yes
- WARNING CA Proposition 65 Message: Warning: Cancer And Reproductive Harm - Www.p65warnings.ca.gov
Features:
- 1 11/16 in. Throttle Bore Size
- 22-74 Primary Jet
- 22-84 Secondary Jet
- 26-70 Idle Bleed
- 26-70 Inter. Bleed
- 26-33 Hi Speed Bleed
- 25-45 Power Valve
- 18-2 Needle And Seat
- Gas Fuel
Quick Fuel Technologys new Street-Q carburetor is intended to deliver legendary Q-Series performance to hardcore street enthusiasts at a reduced price. The major differences between the Street-Q and the race-bred Q-Series is the substitution of cast metering blocks and a cast throttle body in place of fully-machined billet components. All of the critical functionality is retained - 2-circuit metering, downleg boosters, changeable idle and high-speed air bleeds and 4-corner idle. A universal throttle lever design accommodates Ford A/T kickdowns, 700-R4 bracket mounting holes and the ability to mount brackets for Chrysler vehicles. Available sizes include 650, 750, 850, and 950cfm for mechanical secondary models and a 750 vacuum secondary is also offered. Lightweight die-cast aluminum components Changeable idle and high-speed air bleeds Vacuum & mechanical secondary models2-circuit metering - 4-Corner idle systemDownleg boosters Universal throttle lever design fits Ford A/T Kickdown, 700-R4 mounting holes - accepts brackets for Chrysler vehicles

Fitment Warning:
This is a Universal/Non Application Specific Product. To install this part, you made need to cut, weld, or make other modifications to your vehicle.

Brand: Quick Fuel Technology

Vehicle

Shop By Brand

Showing Products For 2008 Toyota Avalon Carburetor