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Library: Weber 45 DCOE Setup

This document is released under the terms of the Creative Commons License unless otherwise noted.
Thanks to Skye P. Nott for writing this article.
Last modified 2006-04-02.


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The Weber 45 DCOE is a popular choice for MGB owners looking to unleash a bit more power in the admittedly rather prosaic (but reliable) B-Series engine. This was the carb of choice among factory entries and racers in the heyday of the MGB, and coupled with the reliability inherant in the design, it powered the B to many finishes above more tempermental entries by other sportscar manufacturers of the time. Combined with a large-bore block and a modern high-flow head, the 45DCOE can really make a difference on the dyno. Whether or not this conversion is cost effective considering the expense and the return in HP, is up to you. Under normal driving conditions, it is my opinion that a well-maintained pair of HS4 or HIF4 SU carburetors is just as good, if not better than, a 45DCOE, considering the complication and expense that tuning these race-application carbs can require. If you do not have the expertise or equipment (such as a wide-band oxygen sensor and rolling road) to tune these carbs properly, you may be chasing after settings endlessly - the number of variables in tuning these carbs is large and requires an understanding of the theory of operation. The settings listed here are a starting point only, from which specific modifications will most likely be required.

45 DCOE 152 Carburetor
Part # 19600.060
Special Tuning Kit # C-AJJ 3312

Fig Qty Description Part Number Fig Qty Description Part Number
1 1 Filter Cover 61002.010 46 2 Cup Washer 58000.006
2 1 Filter Cover Gasket 41530.024 47 3 Spring 47600.007
3 1 Filter Element 37022.010 48 2 Vacuum Screw 64590.008
4 1 Jet Inspection Cover 32376.003 49 2 Pump Jet Gasket 41535.021
5 9 Screw 64700.001 50 1 Spring 47605.012
6 1 Jet Inspection Cover Gasket 41550.002 51 1 Spring Plate 52210.006
7 1 Top Cover Gasket 41715.011 52 1 Throttle Stop Screw 64625.012
8 1 Needle Valve 79503.200 53 1 Pump Plunger 58602.003
9 1 Float (plastic) 41030.034 54 2 Starter Valve 64330.003
10 2 Emulsion Tube Holder 52580.001 55 2 Starter Valve Spring 47600.105
11 2 Air Corrector Jet 77401.* 56 2 Idle Mixture Screw 64750.003
12 2 Idle Jet Holder 52585.006 57 2 Pump Jet 76801.*
13 2 Emuslion Tube 61450.* 58 2 Pump Jet Oring 41565.009
14 1 Stud 64955.007 59 2 Pump Jet Cover 61015.008
15 2 Main Jet 73401.* 60 1 Pump Rod Spring 47600.064
16 2 Idle Jet *.* 61 1 Pump Rod 10410.015
17 2 Auxillary Venturi 69602.450 62 2 Starter Jet 75507.085
18 2 Air Horn 52840.001 63 2 Pump Valve Ball 58300.003
19 4 Air Horn nut 34705.004 64 2 Stuffing Ball 52730.001
20 4 Waasher 55525.010 65 2 Retaining Screw 58070.008
21 4 Air Horn Tab 521550.012 66 1 Neddle Valve Gasket 83102.100
22 2 Main Venturi 72116.* 67 1 Fuel Union Gasket 41530.031
23 4 Stud 64955.110 68 1 Fuel Union 10536.035
24 2 Lock Washer 34710.003 69 1 Fuel Union Gasket 41530.024
25 2 Cap 14945.003 70 1 Fuel Union Bolt 12715.008
26 2 Air Bypass Screw 64750.002 71 2 Inspection Cover 61015.009
27 2 Lock Nut 34705.001 72 1 Float Pin 52000.001
28 2 Locking Screw 64830.006 73 1 Cable Clamp 64605.017
31 2 Lock Washer 55520.004 74 2 Starter Air Jet 77505.150
32 2 Throttle Shaft Nut 34710.003 75 1 Top Cover 31734.197
33 2 Throttle Plate 64005.044 76 1 Plate 52130.003
35 4 Throttle Plate Screw 64520.027 77 2 Washer 55510.128
36 1 Cover Gasket 41640.001 78 2 Bearing 32650.001
39 2 Screw 64750.009 79 2 Oring 41575.019
40 2 Screw 64700.004 80 1 Inspection Cover 52135.024
41 1 Pump Cover Gasket 41640.021 81 1 Gasket 41640.021
42 1 Cold Start Unit 32556.018 82 1 Pin 58445.001
43 1 Pump Exhaust Valve 79701.040 83 1 Cover 32374.008
44 2 Idle Mixture Screw Oring 41565.002 84 1 Pump Cam 45082.005
45 1 Throttle Lever 45048.007 85 1 Throttle Shaft 10005.438
        86 1 Washer 55555.010

* Please see Callibrated Parts Listing

Initial 45 DCOE Settings
Main Venturi 36 ? Auxillary Venturi 5.0 mm
Main Jet 1.85 mm Air Corrector Jet 1.60 mm
Emulsion Tuber F16 Idle Jet 0.60/F8
Needle Valve 2.25 mm (spring loaded) Pump Jet 0.60
Pump Exhaust Valve 40 ? Float/Cover Gasket Level 5 mm *
Chokes 40.0 mm    
* When the level between the float and cover gasket is measured, it is important that the float is allowed to hang vertically. A false reading will be obtained if the lid is held horizontally.

When fitting a 45DCOE to the B series engine, a special manifold will be required. The carb itself is mounted on synthetic rubber O-rings ("Thackeray washers") which absorb vibration and prevent the air-fuel mixture from being disturbed. A steady rod should be made up and connected to the rear engine plate.

Your Weber conversion will be most worthwile if you combine it with cylinder head modifications, a free flow exhaust system and a good air filter setup like K&Ns. Tuning is a complex affair and best done on a rolling road.

More information can be found in MG World No.7 (Oct/Nov 1998) and in Lindsay Porter's DIY Guide (available in the Shop.)

Here's another exploded diagram of the 45DCOE:

Article written by Skye P. Nott.





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This page last modified May 09 2009 16:07:20 pm


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