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[Datsun 1200 encyclopedia]

Weber DCOE carburetor

Revision as of 15:22, 17 August 2013; view current revision
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Category: Fuel System

Weber DCOE sidedraft carburetor. The traditional racing carburetor.

Contents

Sizing

Proper sizing is important for good performance:

8114.jpg


For a 1200cc engine at 6000 rpm, it looks like a 26mm venturi is called for, based on this chart and interpolating for 6000 rpm based on the DCOE chart.

Now, looking at the A12 specs, it seems Nissan used the same logic: A12 venturi: 26 mm

See main article: Carburetor Sizing

Jetting

For baseline tuning, follow the recommended jetting from a Haynes Weber carburetor manual, or another Weber book.

I borrowed an excellent book from the library: Weber Carburetors Owners Workshop Manual by Haynes UK. Amazon.com link). It has this in the back. The B210 specs should be a good starting point for a stock A14.

Conversion equipment jet setting Datsun B110 (A12) - single 40 DCOE 2
Choke size27
Aux. venturi 4-5
Main jet 1-10
Emulsion tube F7
Air corrector jet 1-65
Idle jet 0-50 F9
Accel. pump jet 0-50
Accel. pump inlet valve with ex. orifice 0-50
Needle valve 2-00
Datsun B210 & F10 (A14) - single 40 DCOE 2
Choke size33
Aux. venturi 4-5
Main jet 1-30
Emulsion tube F11
Air corrector jet 1-80
Idle jet 0-50 F8
Accel. pump jet 0-60
Accel. pump inlet valve with ex. orifice closed
Needle valve 2-00
Datsun 510 (L16) - single 45 DCOE 13
Choke size33
Aux. venturi 4-5
Main jet 1-30
Emulsion tube F16
Air corrector jet 1-90
Idle jet 0-50 F8
Accel. pump jet 0-50
Accel. pump inlet valve with ex. orifice 0-55
Needle valve 2-25
Datsun 510 (L16) - dual 45 DCOE 12
Choke size32
Aux. venturi 4-5
Main jet 1-35
Emulsion tube F15
Air corrector jet 1-70
Idle jet 0-55 F2
Accel. pump jet 0-40
Accel. pump inlet valve with ex. orifice 0-55
Needle valve 2-00u

Also see discussion Help????? tunning Weber 40 DCOE on a14


40 DCOE-151 redline #19550.174 baseline jetting
32 Venturis
4.5 Aux venturis
115 Main jets
F11 emulsion tubes
200 Air correction jets
45F9 Idle tubes
40 Pump jet
50 Pump exh
1.75 Needle valve
huicho: SINGLE 40 DCOE ON A STOCK A15 ROUND PORT
COMPLETELY STOCK A15 economy version(round port head)
Main Venturi 32
Aux. Venturi 4-5
Main Jet 140
Emulsion Tube F-11
Air Corrector Jet 200
Accel. Pump Jet 60
Accel.Pump Inlet Valve with Ex. Orifice closed
Needle Valve 200
Idle Jet 55F9. 
If you do not use an air filter:
* 180 on the air correctors 
* 130 on the main jets

Process

Start with venturi/choke size. For dual-carbs (one barrel per engine cylinder) 28mm is good for max power with at 6000 RPM with a 1.2-liter engine. Larger venturis will make good power, but with less flexibility (flat spots, poor part-throttle response). See Carburetor Sizing.

Float Settings
Early brass float: 8 to 8.5mm
Late plastic float: 12.5 to 13mm

In DCOE/DCOM series, the main jet should start at 4 x venturi size. For example, with 30mm venturis start with 120 Main Jets.

The Air Correction Jet should be 1.25 to 1.50 of the Main Jets. For 120 main jet, start with 165 Air Jets.

That much is easy (setting the air/fuel ratio which is around 13:1 for all engines). The trickier part, for which tuning to the particular engine is called for, is the transitions:

  • When accelerating the pump jet and duration are the main factors
  • Transition between idle circuit and cruise circuit is controlled by the Emulsion Tubes and Idle Jets. Do not attempt to fudge this by raising or lowering the float level. The Float Level should be set to the Weber specifications before any other tuning is done.

Parts

Also see Intake Manifold

Kit includes manifold, carburetor, gaskets and linkage
[K110-2T.jpg

Weber K110 A12 twin DCOE Pierce Manifolds $1200

Weber K625 A14 single DCOE

* Pierce Manifolds $575
* Alamo $548

Linkage

Linkage depends on the manifold you use.

Twin-Pull with cannon small-diameter rod
2xDCOE.jpg

Redline Weber linkage

Weber Kit
K206.jpg

Custom Linkage

11496.jpg 11497.jpg 11506.jpg

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