Weber DCOE jetting list

[DerSchwede]

Hi gents,

I'm currently building a new engine for my 09/73 3.0Si. The configuration is this:
M30B34 (euro E28 535i), fully reworked
CR 10:1
Schrick 284/280
Hartge header 40mm primaries/51mm secondaries
Double timing chain
Dual 2" exhaust
3x Weber 45DCOE9 with two progression holes and period Alpina style short intake manifolds
Custom airbox with cold air intake

I'm planning to start with the following jetting in the carbs:
Chokes 38
Main jets 155
Air jets 200
E-tube F2
Idle jets 55F8
Pump jets 45
Return valve 60
Needle valve 225

I'll fit an A/F meter to check the setup when ready but thought it would be interesting to see what others with side-draft Weber use in their carbs and what their engine setup is like... So what do you have?

Cheers
Anders

 

[DerSchwede]

Hi,

just got the carbs back from bench-testing before fitting them to the engine. Our mechanic flipped the butterflies and made them into 15/16 instead of 2s. His advice was to start with F9 instead of F2. Hence this is the set-up I'll will start with:

Chokes 38
Main jets 155
Air jets 200
E-tube F9
Idle jets 55F8
Pump jets 45
Return valve 60
Needle valve 225

/A

 

[Stevehose]

What does flipping the butterflies do? Do you have pics of your airbox?

Hi,

just got the carbs back from bench-testing before fitting them to the engine. Our mechanic flipped the butterflies and made them into 15/16 instead of 2s. His advice was to start with F9 instead of F2. Hence this is the set-up I'll will start with:

Chokes 38
Main jets 155
Air jets 200
E-tube F9
Idle jets 55F8
Pump jets 45
Return valve 60
Needle valve 225

/A

 

[DerSchwede]

Hi Steve,

flipping the butterflies makes a small change to the point where the progression circuit starts to act. On the backside of the 45 DCOE-butterflies (I don't know if this is similar to the 40s) there are two shallow slots that point towards the progression holes, if you flip the butterflies these will point down instead. These 45DCOE9 have 78 deg butterflies, I think the 40s have around 83-84 deg right?

I'll build the airbox when the engine's in the car, making the size and shape depending on how much space there is left... I ordered sheet aluminium for this purpose and will try to make something similar to the Aston DB4/5/6 airbox with an air filter and cold air intake somewhere below/in front of of the battery.

Last Weekend I got hold of an NK brake booster (2000TiLux) since that one has a threaded rod (which the Ti/Tii boosters out there don't) I shortened the adjusting rod from the E3 setup by 60 mm and machined and threaded the end M10 again. Now it measures 365 mm from the back face of the brake booster to the centre of the fork at the pedal end - like in any LHD E3/E9 setup. Almost plug-and-play ;-)

I'll post some pictures when I'm that far.

/A

 

[Stevehose]

I've not seen slotted butterflies before - makes sense. I think most others are 79.5 degree. Gary (m5bb here) has 45's on a modified engine, perhaps some knowledge could be shared both ways there, he's still fiddling with jetting.

Interesting project!