# Weber question.



## 81type53 (Jun 2, 2008)

I have Dual Weber 45 DCOE's on a .20 overbore 2L 16V Motor with a ported head etc. etc. At Idle my A/F Is 13.5-14 When I'm Just on the throttle It leans out and I get past that In a second and then I'm fine and It runs like Mad. In fifth gear when I'm cruising and barely on the gas, same thing It leans out. Anybody run Into this problem with Webers, Is It a normal Weber trait? Should I move to a larger Idle Jet? Most people, Tech support Is telling me to do that. Any Weber experts want to chime In? Carbs have about 250 miles on them since new.


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## antichristonwheels (Jun 14, 2001)

*Re: Weber question. (81type53)*

I would do what tech support suggested. How many turns out are your mixture screws? what is your current jetting?


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## 81type53 (Jun 2, 2008)

*Re: Weber question. (antichristonwheels)*

Two and a quarter turns and I think my Idles are 55's. I have someone doing the the fine tuning for me so I do not mess It up. Idle Jet prob.? Yes.


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## Big CADDY (Aug 28, 2001)

*Re: Weber question. (81type53)*

are you running stacks? are you running Air cleaners?
Carbs if pointing forwards will get all screwey from the air coming in from the grill. 
Try putting a piece of card board on your grill about where the carbs would be. smooths it right out. if it works....... which it will, get some air cleaners or a plenum
55s seem like the right size.


_Modified by Big CADDY at 7:56 PM 4-15-2010_


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## ABA Scirocco (May 30, 2001)

*Re: Weber question. (Big CADDY)*

There's something going on with the off-idle progression, the idle jets are largely responsible for this. The Idle jet numbers consist of two parts, the jet size and the air bleed so the numbers look like 55F8 or 55F9 both jets have the same size bores but the F9 series of jets give a richer mixture than the F8 series of the same size. For some weird reason the F numbers are not sequential from lean to rich, see the list at the bottom of this excerpt, Idle Jet selection
Idle jets cause a lot of confusion; although their name suggests that they govern the idle mixture, this is incorrect. It is true that the fuel consumed at idle is drawn through the idle jet, but the idle mixture is metered not by these jets, but by the idle volume screws mounted on top of each barrel. The idle jets control the critical off-idle progression between closed throttle and the main jet circuit, it is this part throttle operation which is so important to smooth progression between closed throttle and acceleration and for part throttle driving. If this circuit is too weak then the engine will stutter or nosedive when opening the throttle, too rich and the engine will hunt and surge especially when hot. The technique for establishing the correct idle jet size is detailed later, but as a starting point 40/45f9 idle jets for a 1600 engine 45/50 f9 for an 1800 and 50/55f9 for a 2000 will get you out of jail free.
Below is a chart showing approximate idle jet sizes for given engine sizes, this assumes one carb barrel per inlet port E.G. two DCOEs.
Engine size Idle jet size
1600cc 40/45
1800cc 45/50
2000cc 50/55
2100cc 55/60
Establishing the correct idle jet for a given engine is not easy but usually an approximation will make the car acceptably driveable. If the progression is weak then the engine will nosedive when moving the accelerator from smaller to larger throttle openings. A certain amount of change (richer/weaker) to progression can be achieved by varying the air jet size on the idle jet; this alters the amount of air that is emulsified with the fuel drawn through the idle jet. If this does not richen the progression sufficiently then the next jet size up, with the same air bleed should be tried. Below is a small chart showing the most commonly used air size designations, running from weak to rich. Generally speaking start your selection with an F9 air bleed.
Weaker Normal Rich
F3 , F1 , F7 , F5 ,F2-F4 ,F13 ,F8-F11-F14,F9 , F12 , F6
The ones in normal use are F2,F8,F9 and F6


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## ABA Scirocco (May 30, 2001)

*Re: Weber question. (ABA Scirocco)*

Almost forgot, that excerpt came from HERE.


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## ABA Scirocco (May 30, 2001)

*Re: Weber question. (ABA Scirocco)*

A few minutes ago, I was talking to my mechanic, he's a expert at tuning Webers for maximum performance so I mentioned your problem, he said the problem could likely be corrected with an idle jet change. He also said there's one very important thing to check before you start messing around with idle jets and that's the position of the throttle plate at idle. In this picture of the DCOE idle circuit, you can see the progression ports just above and to the right of the throttle plate, it's critical that the throttle plates be adjusted so that at idle they do NOT advance past the first progression port, if they do, it'd be next to impossible to find idle jets that work properly.








In this picture, air is blue, fuel is yellow and the air/fuel emulsion is green. The plug directly above the progression ports can be removed to check the position of the throttle plate with respect to the ports.



_Modified by ABA Scirocco at 8:25 PM 4-15-2010_


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## brownhound (Mar 22, 2007)

*Re: Weber question. (Big CADDY)*

Here's a pic of 81type53's air horns/air box set-up.


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## Big CADDY (Aug 28, 2001)

*Re: Weber question. (brownhound)*

well if that is his air box my theory is irrelevant
have they been sync'd ?
Fuel pressure?
ABA has some very good points above, as always... 
Are you sure they are 55 jets and they haven't been drilled out?
Can you get me info on his Crank position sensor and coil pack setup. I like that.


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## 81type53 (Jun 2, 2008)

*Re: Weber question. (Big CADDY)*

They have been sync'd and they are f855's which seem to be corect for the motor. They Idle and run great but It's the just- on throttle problem which needs to fixed. The tech who Is tuning them has 25 years of Weber Experience and works on Formula One resto's etc. He Is going to the next Idle Jet and we'll see from there. Thanks for all of the Input and to ABA, I printed your Input and am bringing it down to the shop today. The Setup I s an Electromotive XDI with Electromotive DFU etc. Car Is a complete Animal, I Just wan't to try and get it as perfect as possible. C.


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## 81type53 (Jun 2, 2008)

*Re: Weber question. (81type53)*

Solved with changing out the Idles to larger Jet. Thanks for the help.


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## ABA Scirocco (May 30, 2001)

*Re: Weber question. (81type53)*


_Quote, originally posted by *81type53* »_Solved with changing out the Idles to larger Jet. Thanks for the help.

http://****************.com/smile/emthup.gif http://****************.com/smile/emthup.gif


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