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Discussion Starter #1
I have recently bought a pair of Weber 40 type 2’s to fit to my Series II 2L Spider - the plan is to have a normal street car which will also be fun to drive on the occasional twisty road.

I have read several posts on Weber 40 DCOE jetting and have managed to answer most of my own questions, but I am still a little confused by the idle jet settings.

The carbs came with the following:
Choke 30
Secondary Venturi 4.5
Main jets 125
Air correction 160
Emulsion tube F7
Pump jet 40
Starter jet 65F5
Inlet/Exhaust valve (in bottom of well) 50
Inlet needle jet 175
Float 26g

But the idle jets are a mix of 55F8 and 45F8 - one of each in each carb.
So my question is whether I should buy 2 more 55’s or 2 more 45’s, or just average it out and buy 4 50F8?

Many thanks to all those whose posts I have found so helpful - especially Gordon Raymond, AlfaParticle and Alfa7.

Kind regards

James
1972 Series II Spider
1974 2L GTV
 

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I have weaned my 2 litre on to 50F8, which are the accepted standard. I used 55F8 for a while (too rich) to overcome a stumble problem, but that's gone now. Mine are DCOE 44/45 from a 1600, which I have adapted (30 to 32 chokes), 117 to 135 mains.
 

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By "type 2" do you mean 40DCOE2 or the later, emissions type such as 40DCOE72/73, 40DCOE116/117, etc?
 

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Discussion Starter #4
Hi AlfaParticle
Many thanks for getting back to me - these are actually 40DCOE4 carburettors (numbers 42616 and 43325) - apologies for the typing mistake
Kind regards
James
 

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I agree with Malcolm that 50F8 is the normal idle jet for a 2L motor.
F7 is an unusual emulsion tube for an Alfa Nord. F9, F11 or F16 are the ones that are commonly used.
30 mm chokes will cost you some top end power compared to 32's but the driveability and throttle response should be very good. I would expect the best main jet to be 125 for a 2L motor with 30 mm chokes.
 

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In general I agree with Ed. But if you look at the "Factory jetting" you have to keep in mind that the 2 Liter Factory WEBER jetting was to work with the better 1054803200 01 cams not the anemic 10520 03200 01 Spuica/Bosch junk we got in the USA..
I built a set of 40 DCOE 18s (Italian) for 2 liter application and I used 115 mains, F 16 E tubes, 50 F9 idle jets and 155 air correcter jets with 33mm reshaped choke tubes as the starting point for tuning.
If using any carb setup, start fairley close, then fine tune AFTER you install a wide band O2 meter to get it right on....
 

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James is in the UK and my assumption is that he has Euro cams. My rule of thumb is that a 2 mm change in choke size requires a change of 5 in main jet size. 130 is usually a good starting point for 32 mm chokes so I suggested 125 for his 30 mm chokes. 40DCOE4's were OE for some 1600 Alfa's.
 

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Discussion Starter #8
Thank you everyone for your responses - 50F8 seems to be the consensus and now have 4 on order - plan will be to fit them over the weekend - will be using Colortune to get in the ball park and to visit a rolling road to dial them in.

Once again many thanks for all your help
Kind regards
James
 

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I am running 50F8 idle jets in our Weber carbed spider. Burbles at idle, gas mileage is poor, mixture screws are 2 1/2 out
 

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gas mileage is poor
How poor? My mildly tuned motor got around 26 mpg average and about 28 mpg on a long drive.
I agree with 50F8 or 50F11 for those carbs.
 

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Something is seriously wrong. Are you sure that you don't have a fuel leak?
A friend had lousy gas mileage with a GTV that he bought and I think the problem was with the Aliquati cams that were in it.
For comparison my 45DCOE152's have 60F9 idle jets and I get 25 mpg or thereabouts on a long run and over 20 mpg average.
What kind of ignition system do you have?
 

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Agreed, something is wrong. She starts well, idles good at 900 rpms when warm, transitions good and pulls good to 6,000 rpms. I am running a stock points distributor. No fuel leakage. A year or so ago I had them rebuilt by a guy in S Dakota. Carbs are synched well
 

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When I tried different advance curves in my 123 distributor I found that the ones with faster advance curves gave better fuel consumption. Also higher energy sparks will ignite leaner mixtures that otherwise cause misfires. Webers do not produce a constant AFR and to eliminate misfires you lower the overall AFR until the peaks do not cause hesitation or poor throttle response but the price you pay is a richer mixture everywhere else. An improved ignition may well allow you to use leaner jetting while still having good driveability.
Cam timing also has an effect. Reversion in the intake occurs just before the intake valve closes and the later the closing the more reversion. You have to check for piston to valve clearance when advancing the intake cam. Stock cams and pistons can probably allow the intake LC to be safely moved to about 98 degrees and may improve both torque and fuel consumption.
 

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Any ideas regarding Colortune? good information Y/N? I have a Centerline electronic distributor on the shelf, but from what I can tell the points setup is working fine.
 

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Colortune is popular in the UK. I don't know for sure but I think that you can only use it when the car is stationary which means at very light throttle. It should be good for adjusting the idle mixture and maybe gentle low speed driving.
 

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Thank you, I will give the Colortune a shot. The idle jets are 50F8, from what I can tell they are correct for a 2 liter Alfa street motor, what would be more towards the lean side?
 

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50F11 is one step leaner.
 
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