Weber DCOE 45 carburettors

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Graham Stewart
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Weber DCOE 45 carburettors

Post by Graham Stewart » December 14th, 2010, 9:57 pm

I'm planning on purchasing a pair of Weber DCOE 45s for my Lancia Beta 2 litre before VAT goes up to 20% in January, and am trying to decide whether I go for the standard 3 hole progression type (part number 1960006000) or the newer 4 hole progression type (part number 1960006200). On Guy's advice, I contacted Northampton Motorsports and this was their comment:

There are a number of variations on the DCOE carb. The 6000 has the standard 3 progression holes whilst the 6200 has 4. we do find that the 4 hole carb is better for most applications and the price is the same for both variants.

I specifically stated in my question that it was for use on an 8v TC 2 litre Lancia, but no specific recommendation was forthcoming. Have any forum members any comments to make on suitability for my application? I'm currently gathering the parts needed to upgrade my 2 litre TC to Guy's 'fast road tune' specification; standard cams, twin DCOE 45 carbs (36mm choke) with manifold to suit, ported head, balanced crank/flywheel. approx 9.3:1 CR.

I need to make a purchase before 4th January to miss the VAT hike, so any guidance is welcome.

ace124
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Re: Weber DCOE 45 carburettors

Post by ace124 » December 15th, 2010, 6:50 am

I suggest you opt for the 4 progression hole version. You will find the 3 hole version has a sizable gap between the throttle plates and the 1st progression hole. This leads to a lean spot that cannot be tuned out. I have the 3 hole version and although i get them to idle perfectly with 55F9 idle jets: AFR of 14-15:1, as soon as i touch the accelerator in low load cruise they run lean no matter what jetting i try at about 17-18:1 AFR. This is because like i said the progression circuit is still not exposed. As you open the throttle more then you get it to richen up as the holes are exposed, by then its onto the mains and OK.
Solution is to drill a 4th hole under the butterfly's. I did it for a friend recently and his runs better, but i have not done mine yet as im thinking of throttle body injection now.

Bottom line: 4 hole prog circuit for Fiats and Alfas.

Guy Croft
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Re: Weber DCOE 45 carburettors

Post by Guy Croft » December 15th, 2010, 12:59 pm

From a purely personal perspective I have worked with a lot of different DCOE carbs and never had a progression problem that could not be tuned out. I've used F8 and F9 idle jet holders variously where alterations to the engine setup and pump jets could not fix a hesitation around 2500-3000 rpm.

There are more causes for hesitation (flat spot) than merely the progression drillings, I would not place much stock on how many there were, seriously...


G

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