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Weber 28/36 Manifold & Jetting

B

Barrythebrit

Donation Time
I have Weber DCD on my Series V, which at some point has had a Series IV engine put in it:mad:
Question .1. I can see that the manifold has connection to be water heated, is this something worth doing, I have it installed at the moment with no heating to the manifold (ie Blanked off on the Manifold) and seems to be running O.K up to the second choke which brings me to the next question...

Question .2. Does anyone know the jetting for a Weber 28-36 DCD on a 1600 Alpine Series IV engine? I am at sea level (Ireland so... not to warm) and have a Ramflo air filter attached.

Any advise would be very much appreciated.:)

Barry
 
R

RootesRacer

Donation Time
Barrythebrit said:
I have Weber DCD on my Series V, which at some point has had a Series IV engine put in it:mad:
Question .1. I can see that the manifold has connection to be water heated, is this something worth doing, I have it installed at the moment with no heating to the manifold (ie Blanked off on the Manifold) and seems to be running O.K up to the second choke which brings me to the next question...

Question .2. Does anyone know the jetting for a Weber 28-36 DCD on a 1600 Alpine Series IV engine? I am at sea level (Ireland so... not to warm) and have a Ramflo air filter attached.

Any advise would be very much appreciated.:)

Barry
Click to expand...

1) The water helps for cold weather operation as it heats the intake to prevent fuel fallout in freezing conditions.
If you dont use the car in very cold or cold humid conditions, you really dont need the water connection as it lowers engine power by reducing the volumetric efficiency of the engine.

2) The jetting depends to the greatest degree on the size of the primary and secondary venturies. The DGV/DFV settings are well understood and a baseline set of jets is known. The DCD however is a different carb so without knowing the venturi/choke sizes one cant venture a guess.
 
B

Barrythebrit

Donation Time
1) Excellent... I will leave the heating off the manifold and see how I get on.

2) Primary Venturi is 26, the secondary Venturi is 27 not sure about choke sizes.
but here's what I have currently:
Primary/
main Jet 140
Emulsion F30
Air Correct 220
Idle jet 50

Secondary
Main Jet 160
EmulsionF30
Air Correct180
Idle jet 170

Runs fine up to about 3500RPM on moderate throttle then seems to run too lean. Also seem to struggle when you put your foot to the floor.(ie when the Primary I almost fully open)
 
Eleven

Eleven

Platinum Level Sponsor
Barry,
I do not have a heater on mine and wish I did. I am in Seattle and our weather is not that different than yours. The car will run fine but take freaking forever to get off the choke. If I could, I would use it myself. Having said that, Rootesracer has more experience than I do with Alpines. One my golf courses I have to play is Old Head. Was in Ireland 3 years ago and got to see it. Since my wife does not always view Golf as a vacation activity, view is as far as I got!
 
R

RootesRacer

Donation Time
Barrythebrit said:
1) Excellent... I will leave the heating off the manifold and see how I get on.

2) Primary Venturi is 26, the secondary Venturi is 27 not sure about choke sizes.
but here's what I have currently:
Primary/
main Jet 140
Emulsion F30
Air Correct 220
Idle jet 50

Secondary
Main Jet 160
EmulsionF30
Air Correct180
Idle jet 170

Runs fine up to about 3500RPM on moderate throttle then seems to run too lean. Also seem to struggle when you put your foot to the floor.(ie when the Primary I almost fully open)
Click to expand...

There should be more or less a constant ratio between the main jet to the choke size. In your case, the primary main to choke ratio is quite rich.
With 26mm and 27mm chokes, I would expect similar sized jets, often with the secondary a tad higher ratio so it has a slightly richer signal when the throttle is opened. The zenith DD carbs used on earlier models have a similar sized choke, and they run 115 to 125 on the main jets. Based on that I'm kinda surprised you think it runs lean...

The F30 emulsion is a mystery to me as I dont have any DCD data.
Most webers have a relatively common emulsion, often called an F9 which is well understood and works across many carb types even though they differ a bit from model to model.

If the idle jet is in fact 170 on the secondary, that would be very odd.
The secondary idle jet does fuel the progression, but you should never need that level of jet for that since the secondary fuel progression is only in play for precious few degrees of throttle beginning when the secondary begins to open.
 
B

Barrythebrit

Donation Time
Thanks RootesRacer, there was a typo... the secondary idle is 70.
Think I better order some smaller main jets and see how I get on.
From what I can find the F30 Emulsion tube was specific to the DCD and DCZ, although saying that I can see that a F9 emulsion tube is listed for the DCD and is described as follows "Tubes with many orifices for high RPM mixture richness reduction when air bleed jet is larger than 2.00mm"
I will give the F9's a go.

Eleven - sorry to hear you did not get to play Old Head... I am not a golf fan (yet) but those greens look perfect for doing some doughnuts on in the Sunbeam!!
I hope that drinking lots of Guinness was considered a vacation activity!:)
 
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