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|
|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|
|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|
|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|
|35||4||Throttle Plate Screw||64520.027||77||2||Washer||55510.128|
|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|
|* Please see Calibrated Parts Listing||86||1||Washer||55555.010|
Weber 45 DCOE Initial Settings for MGB
|45 DCOE Initial 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 *|
|* 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.
Weber 45 DCOE Carburetor Notes
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 Book - available in the MGExp Store
vacuum advance hose that goes down to the distributor. I hooked it
up to the intake manifold (per advice from the guy I bought them
from - but doesn't vacuum drop on acceleration??? It seems I
would tap in on the carb side, maybe even near the air horns. There
are what appear to be knock-out plugs near the idle adjustment
screws; additionally, there are plugs on the carb body near where the
air horns hook up (sort of on the outer/lower side (about 270
degrees on the right side when viewing from the intake or air horn
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