Weber Carburetor Jetting Calculator - Engine Database Edition

🚗 Select Make & Engine (Auto-fills specs)

Make

Engine

💡 Pick a make first, then choose an engine. Specs auto-fill after engine selection, including an approximate stock peak-power RPM, and you can still override them below.

Engine Configuration

Displacement (cc)

Cylinders

Peak Power RPM

Cam Profile

Carburetor Setup

Confirm the cam profile first, then choose the suggested carb setup or override it manually.

Carburetor Specs

Main Venturi/Choke (mm)

DCOE Body

Idle Air Bleed

Altitude (ft)

Temp (°F)

⚠️ High altitude: Baseline applies a 2% main jet reduction per 1000ft above sea level.

Available Parts / Forced Overrides

Leave these blank for the normal recommendation. Fill them in when you only have certain jets on hand and the calculator will estimate whether the rest of the combo can compensate.

Available Main Jet

Available Air Corrector

Available Idle Jet

Available Pump Jet

Available Secondary Air

Use forced jet values only when you need to work with the parts you already own.

📊 Recommended Baseline

Custom setup • 2000cc • 4 Cyl • 6000 RPM • Street Perf

Selected Carburetor Setup

DCOE Single

One DCOE body with two throats. Baseline shown as a per-venturi recommendation where applicable.

1 carb / 2 throats 1000cc per venturi Per-venturi baseline

Configuration Health Score

Good

Baseline configuration is well matched and should respond normally to fine-tuning.

No forced parts are active.

📐 Technical Formulas

Main Jet: Venturi × 4 baseline, then altitude/cam adjustments, then rounded to the nearest 5.

34 × 4 = 136 → street cam +0 → round = 135

Air Corrector: Main Jet + 50, rounded to the nearest 5.

135 + 50 = 185

Emulsion Tube by Cylinder Size:

<325cc: F11 | 325-400cc: F15
400-475cc: F16 | >475cc: F2

📝 Advisory Notes

Setup: DCOE Single • Weber DCOE / sidedraft • 45 body

Suggested venturi: 34mm

Baseline recommendations shown. Temperature and carb body inputs are advisory only.

📈 Estimated AFR Chart

Estimated by operating zone from the selected baseline jetting. This is a directional tuning aid, not a substitute for a wideband.

Estimated AFR trend will appear here after calculation.

Target range Estimated AFR line Operating point

Targets are biased toward safe street/performance baselines: slightly leaner at cruise, richer under acceleration and WOT.

Family	Typical Use	Calculator Coverage
DCOE / sidedraft	Individual-runner side-draft setups on naturally aspirated or period-style performance builds.	Supports single, twin, and triple carb layouts, removable chokes, main jets, air correctors, idle jets, emulsion tubes, pump jets, auxiliary venturis, and needle valves.
IDF / downdraft	Downdraft dual-throat performance carburetors on manifolds for upright or downdraft applications.	Supports single and twin carb layouts, removable vents, main jets, air correctors, idle jets, emulsion tubes, pump jets, boosters, and needle valves.
32/36 progressive	Street-oriented single-carb conversions with fixed progressive primary/secondary throttles.	Supports common 32/36 models, fixed venturi pairs, primary/secondary mains, primary/secondary air correctors, idle jet, emulsion tube family, and needle valve suggestions.

Item	Range	Result
Main Jet	Venturi × 4 baseline, then altitude/cam correction	Rounded to nearest 5, clamped to 115-180
Air Corrector	Final main + 50	Rounded to nearest 5
Emulsion Tube	<325cc / 325-399 / 400-474 / 475cc+	F11 / F15 / F16 / F2
Idle Jet Size	≤1600 / ≤1800 / ≤2000 / ≤2200 / 2201cc+ effective displacement	40 / 45 / 50 / 55 / 60
Pump Jet	Small engine / street / race	35 / 40 / 45
Auxiliary Venturi	Venturi ≤30 / 32-36 / ≥38	4.0 / 4.5 / 5.0
Typical Choke Availability by Body	40 / 45 / 48 body	28-36 / 32-40 / 36-42mm typical practical range

Per-Cylinder / Rotor Capacity	Base Choke Suggestion	RPM Modifier
Below 300cc	28mm	Add 2mm at 7500 RPM or above. Subtract 2mm at 5500 RPM or below. Final result is capped between 28mm and 40mm.
300-374cc	30mm
375-449cc	32mm
450-524cc	34mm
525-649cc	36mm
650cc and above	38mm

Item	Range	Result
Main Jet	Venturi × 4.1 baseline, then altitude/cam correction	Rounded to nearest 5, clamped to 115-190
Air Corrector	Final main + 55	Rounded to nearest 5
Emulsion Tube	<350cc / 350-449 / 450cc+	F11 / F7 / F2
Idle Jet Size	≤1600 / ≤1900 / ≤2200 / ≤2600 / 2601cc+ effective displacement	45 / 50 / 52 / 55 / 60
Pump Jet	Small engine / street / race	40 / 45 / 50
Booster / Aux	Venturi ≤30 / 32-36 / ≥38	4.0 / 4.5 / 5.0 reference
Typical Choke Availability by Body	40 / 44 / 48 body	28-36 / 32-40 / 36-44mm typical practical range

Item	Range	Result
Venturi Pair	Street baseline / hotter street-performance	26/27mm / 27/29mm
Primary Main Jet	Engine-size baseline plus altitude/cam correction	Rounded to nearest 5, clamped to 125-165
Secondary Main Jet	Primary main + 10 to 15	Rounded to nearest 5, clamped to 135-175
Primary / Secondary Air	Primary main + 35 / secondary main + 45	Rounded to nearest 5
Idle Jet	≤1600 / ≤2000 / 2001cc+	50 / 55 / 60
Emulsion Series	Street / broad baseline / sportier transition	F50 / F66 / F6

Reference Topic	Range / Selection	Advisory
Altitude	Above sea level	Baseline logic reduces the main jet by 2% per 1000 feet. A visible warning is shown above 2000 feet.
Temperature	40°F and below	Colder air is denser, so real-world tuning often ends up slightly richer than the baseline.
Temperature	41°F to 94°F	Moderate temperature range; no extra numerical correction is applied.
Temperature	95°F and above	Hotter air is thinner, so real-world tuning often ends up slightly leaner than the baseline.
DCOE / IDF Body	40 body with venturi above 34mm	Unusual pairing; verify signal strength and throttle response.
DCOE / IDF Body	45 body with venturi below 32mm or 44 IDF with very small vents	Can work, but low-speed signal may be softer than a 40 DCOE.
DCOE / IDF Body	48 body with venturi below 36mm	Usually happier with larger chokes and higher-RPM combinations.
32/36 Progressive	Any listed model	Primary barrels handle cruise and progression; secondary barrels come in later, so response depends heavily on linkage, manifold heat, and distributor curve.

🔧 Weber Carburetor Jetting Calculator

📊 Recommended Baseline

DCOE Single

📐 Technical Formulas

📝 Advisory Notes

📈 Estimated AFR Chart