# Weber DCOE sync and tuning questions



## machschnelGTI (Jun 28, 2004)

I have a brand new set of Weber 48s on a 1.8L 8V motor, and I'm having some trouble syncronizing them. I have 3 barrels reading 8in/hg, and one barrel reading 10in/hg. I'm thinking that the throttle shaft in the troubled carb is twisted, but I don't understand how, they're more or less brand new. I've run about 5 gallons of fuel through them during testing and tuning. The linkage I set up pulls from the center of the two carbs. I tried twisting the shaft a bit by hand, using what I thought was quite a bit of force, and got no change. Am I missing something? All the vacuum readings are stable, so I don't have a tight valve I don't think.


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## NORSK (Feb 26, 2006)

*Re: Weber DCOE sync and tuning questions (machschnelGTI)*

Hmmm,very strange that 1 barrel pull more air than all the 3 others.
If it is DCOE carbs you can take of the screw next to the mixture screw and you can see the plates through some tiny holes.
These holes are calibrated good enough to make a roughly adjustment,and you should be able to see if the axle is bent from there.
By the way,which barrel pull more air than the 3 others?


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## machschnelGTI (Jun 28, 2004)

*Re: Weber DCOE sync and tuning questions (NORSK)*

The #4 barrel pulls more. I'll pull out the screws and check it out.


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## machschnelGTI (Jun 28, 2004)

*Re: Weber DCOE sync and tuning questions (machschnelGTI)*

Pulled both screws, its hard to see the plate position because of my airbox, but with a mirror, they look pretty close. I'll keep screwing with it and see what I can come up with.


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## candm (Apr 27, 2003)

*Re: Weber DCOE sync and tuning questions (machschnelGTI)*

you could try the auxilliary air screw which is under i white cap on newer style sidedraughts. typically they are not touched but were used to fine tune idle adjustment and balance. good luck


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## Korijo (Dec 23, 2003)

*Re: Weber DCOE sync and tuning questions (machschnelGTI)*

dont you think dual 48's is too much for that 1.8? dual 40's or a single 45, with proper jetting, are good up to 200 HP!


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## NORSK (Feb 26, 2006)

*Re: Weber DCOE sync and tuning questions (machschnelGTI)*

Well,if the axle looks ok i really don't know what to suggest.
Maybe you have a leaner idle jet in # 4? Just guessing.
Of course,it could be a mechanical problem,or vacuum leaks,but i really doubt you have trouble with 3 cylinders at the same time.
If it is a solid head,maybe # 4 has a different clearance,but as i said,i am only guessing wild here.
Different spark plug gap in #4


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## NORSK (Feb 26, 2006)

*Re: Weber DCOE sync and tuning questions (Korijo)*


_Quote, originally posted by *Korijo* »_dont you think dual 48's is too much for that 1.8? dual 40's or a single 45, with proper jetting, are good up to 200 HP!









Formula Atlantis used dual 48dcoe with 42mm choke's on a 1600cc,200hp on dual 40's or a single 45








With a heavy dose of Nitrous maybe..........


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## machschnelGTI (Jun 28, 2004)

*Re: Weber DCOE sync and tuning questions (NORSK)*

The motor turns 9000.....10 if I need to stretch it, so 48s are fine. I'm using a 4.81 final drive in a 9A box so I need the RPMs. I checked in the little inspection holes, and the plate positions are dead even all the way across. Just for grins, I did a compression test, I was 200-210 all the way across, and my leakdown was 4-5%. I rechecked the valve clearance and I had a couple that were a few thou loose, so I readjusted them to make 'em perfect. Either way, it doesn't appear as if 1 cylinder is performing better or worse than all the rest. For all practical purposes, everything is dead even. I'm still about 2 or 3 inches higher on the #4....I don't get it. I'll call weber in the morning and ask them....hell I just wrote them a check for $1200 for the setup so they owe me a little customer support. If I don't get anywhere, I'll run it like this at the track next weekend and see how it works. 


_Modified by machschnelGTI at 10:11 PM 4-30-2006_


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## NORSK (Feb 26, 2006)

*Re: Weber DCOE sync and tuning questions (machschnelGTI)*

What i would suggest if you don't have it allready,is a exhaust temp probe for each cylinder.
Very handy when tuning carb engine's.


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## orange_rabbit82 (Mar 22, 2002)

*Re: Weber DCOE sync and tuning questions (NORSK)*

where is your vaccum line for the brake booster tapped into....if it is just the one runner then there is your problem


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## NORSK (Feb 26, 2006)

*Re: Weber DCOE sync and tuning questions (orange_rabbit82)*


_Quote, originally posted by *orange_rabbit82* »_where is your vaccum line for the brake booster tapped into....if it is just the one runner then there is your problem

He said one carb was pulling MORE than the 3 others
If it was pulling LESS i would agree with you


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## machschnelGTI (Jun 28, 2004)

*Re: Weber DCOE sync and tuning questions (NORSK)*

I work about 2 miles from Weber Norh America, so I brought them down there....they guy kept the for 2 days and played with them, told me my linkage was the problem, and gave them back. I fabbed up a new linkage per his instructions, and they're still screwed up. I give up. Going with EFI now and moving up to the next class I guess.


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## MkIIRoc (Feb 20, 2005)

want to sell me the 48's? I got 20 bucks and some slightly used oil


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## airNwater (Dec 9, 2003)

*Re: Weber DCOE sync and tuning questions (machschnelGTI)*


_Quote, originally posted by *machschnelGTI* »_I have a brand new set of Weber 48s on a 1.8L 8V motor, and I'm having some trouble syncronizing them. I have 3 barrels reading 8in/hg, and one barrel reading 10in/hg. I'm thinking that the throttle shaft in the troubled carb is twisted, but I don't understand how, they're more or less brand new. I've run about 5 gallons of fuel through them during testing and tuning. The linkage I set up pulls from the center of the two carbs. I tried twisting the shaft a bit by hand, using what I thought was quite a bit of force, and got no change. Am I missing something? All the vacuum readings are stable, so I don't have a tight valve I don't think. 

When you put linkage on did you use two wrenches to tighten the arms onto the shaft? On on the other side to hold the shaft? It's a sure way to twist the shafts. Take a look at the throttle stops on the carbs. Having too much throttle could also screrw up the shafts because the carbs have the stops on one end right? One carb will be hitting the stop near you center pull and the other will hit the stop all the way across the other side of the carb. This is where you can jack up shafts. If it hits the stop the only thing that can give is twist in the shaft. You are sycning without any throttle cable right? You can bring a low barrel up, but the other way around tells me that you shaft might be bent. I would take the carbs off and turn the throttle stops in untill the butterflys rest on the bores. Then take a feeler gauge and see if one gap is larger than the other. Are your stacks sealed at the base?


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## SUSPENDED (May 19, 2004)

*Re: Weber DCOE sync and tuning questions (machschnelGTI)*

switch them around, see if it does it still. trial and error


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## machschnelGTI (Jun 28, 2004)

*Re: Weber DCOE sync and tuning questions (SUSPENDED)*

the shafts aren't twisted....I didn't use two wrenches to tighten the levers. I've switched the carbs, and the problem followed the carbs. Typical italian crap. I should have remembered the fiat when I made my decision to buy webers, I probably wouldn't have done it.


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## chickenfriend (Jan 31, 2005)

*Re: Weber DCOE sync and tuning questions (machschnelGTI)*

I'd bet it is a QC problem with the carbs.
Is the throttle plate of the bore in question equally centered with the other plates?
You might need to re-center it, or re-center them all together.
Make sure the factory didn't do something stupid like put on a wrong sized throttle plate.



_Modified by chickenfriend at 8:54 AM 6-25-2006_


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