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Folks,
Lately I've been working on a 1300N equipped with a 36DCD and I've noticed the robust RPM increase when using the "choke knob" on the dash when start and run.
My car is a '60 spider abnormale 1600 with 40DCOEs. Pulling the choke knob on twin webers results in some enrichment but no real increase in RPM.
Should I take a closer look at the DCOEs to see if the start circuits are correct?

Thanks,
Jim
 

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My experience with my two, Weber-equipped 2L cars is that the RPM's do increase when the enrichment devices are pulled. Perhaps the lack of an RPM increase on your 1600 suggests that some other jetting in the idle circuit is off. But I'm just speculating - people with more Weber knowledge than myself should chime in. .

A more practical question might be: "Yea, but how does the 1600 run when it's cold and the "choke" is pulled out?". If it doesn't stall or bog down, then maybe you don't have a problem to solve (though the difference between the two cars is perplexing).
 

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I think that the cold start devices add a fuel/air mixture downstream of the butterfly. More fuel/air mixture = higher rpm.
Also cold engines need more fuel than hot engines and the enriched mixture from the cold start device gets the engine closer to optimum AFR.
 

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On mine, pulling the choke leads to a small increase in idle speed - particularly if the engine isn't running well without it. My understanding is that it's an enrichment device - more fuel, but not (much) more air, so I wouldn't expect an big change in revs. I think some other carb designs combine enrichment with idle speed increase. On mine there is a separate hand throttle lever which can be used to increase the revs.
 

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I was going to start a new thread regarding the high idle when choke cable is pulled out. The '85 2L spider with Weber conversion is finally idling good, transitioning good and pulls good, but I cannot get the idle speed to increase when the engine is cold. After a few minutes of running the engine speed will increase somewhat. Is there an adjustment for the "high idle" when the starter devices are engaged?

thanks

Ranz - I have scoured the Datsun site regarding the DCOE carbs, there take is the starters are almost useless
 

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Is there an adjustment for the "high idle" when the starter devices are engaged?
I don't think so. On the earlier cars boosting cold idle was done via the separate throttle knob/lever on the dash (that physically pulled on the throttle assembly.)

I won't say it's useless, but the DCOE starter circuit is not particularly great. It's basically just another set of jets that adds aerated fuel to enrichen things. On the Weber'd Giulia I do find it useful to pull the choke lever about halfway to help with cold starting, but once started I generally push it in pretty quick and just baby the engine with the throttle for a minute. So I'm not sure you're ever going to be able to get the performance you want out of them when cold.

The Dellorto DHLA choke is much more functional and does a good job of both enrichening the mixture and boosting the idle. I believe these open up a throttle bypass to let more air in (they definitely make a quite loud hissing sound when engaged!)

Honestly having played around with both now I'm pretty convinced the Dellortos are a better carb than Webers overall. It just seems like Dellorto did a lot more development work to make them functional for normal driving.
 

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My Weber equipped GTV has two levers, one is for enrichment, the other is a hand throttle, which can be used to boost the idle speed
 

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Thanks guys, this spider will be basically a run for ice cream sporting car, summer only, no rain, always garaged, ...
 

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I converted my originally-SPICA '79 Alfetta to dual Weber DCOE40s several years ago, and on my car pulling the choke has very little effect on idle speed, as several others have noted. Tom ("Gubi") wrote "On the Weber'd Giulia I do find it useful to pull the choke lever about halfway to help with cold starting, but once started I generally push it in pretty quick and just baby the engine with the throttle for a minute" - that perfectly sums up my own experience and starting technique.

For what it's worth I've tried several different idle jets (to cure an unrelated stumbling-during-transition problem) and noticed no change in the cold start situation.
 

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For what it's worth I've tried several different idle jets (to cure an unrelated stumbling-during-transition problem) and noticed no change in the cold start situation.
What idle jets did you settle on, may I ask. On my DCOE equipped 2 litre (DCOE 40 44/45), the conventional choice of 50F8 gives me a transitional stumble. Switching to a richer 55F8 fixes it, but quickly soots the plugs
 

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What idle jets did you settle on, may I ask. On my DCOE equipped 2 litre (DCOE 40 44/45), the conventional choice of 50F8 gives me a transitional stumble. Switching to a richer 55F8 fixes it, but quickly soots the plugs
The 2L spider we are working on (stock) runs and transitions good with 55f8. Yes the plugs are black and mixture screws are 2 1/4" turns out. I have spoken with Pegasus, they recommend 60f8. I may just leave "well enough" alone
 

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I ended up with 60f8. The carb conversion kit came equipped with 55f8 and stumble, and I switched early on to 55f9, with a bit less stumble but still present. During my most recent experimentation I tried the following with varying degrees of poor running: 50f8, 55f17, and 55f6, before settling on the 60f8 which seems to be the ticket for my 2.0L Alfetta (with medium-hot cams and Euro cast-iron header exhaust, if it matters). Haven't checked the plugs for soot yet, but I certainly get some of that out the exhaust.
 

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From what I understand the 50, 55,60, .... increase in size as the numbers increase. The f6, f11, f8, .... do not increase or decrease as the numbers increase. Pegasus has been helpful, but tuning the Webers can be tricky
 

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The 2L spider we are working on (stock) runs and transitions good with 55f8. Yes the plugs are black and mixture screws are 2 1/4" turns out. I have spoken with Pegasus, they recommend 60f8. I may just leave "well enough" alone
May I ask what main jets you are running. I went for 135, but maybe 130 would be more suitable?
 

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The first two numbers are the diameter of the fuel orifice. 50 is 0.50 mm. The numbers after the F are cryptic and they define both the air orifices and the internal bore. There are tables that list them from lean to rich.
2L, 4 cylinder motors usually need 50 or 55 fuel orifices in "classic" Webers. "Emissions" Webers take a different series of idle jets where all of the orifices are larger. 60F8 is unusual for a 2L Alfa.
 

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Mal,

The main jets are 120. 2.L spider stock. Runs good, idles good, transitions good.
Those seem surprisingly small. The carbs on mine, which the previous owner tried to carry over from a 1600 had 117 mains with 30 venturis. I upped the venturis to 32 and switched to 135 mains. I heard mention of 132 main for a 2.0L . Small mains could lead to a damaging lean mixture at high speed
 

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Italian Weber 40 DCOE carbs on this 2L spider. I have not done a full speed run/cut the engine at speed/pull the plugs check as yet. But she pulls good, no signs of pinging
 
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