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My 1974 GTV 2000 was converted from SPICA by a PO. The current Weber setup is: 40DCOE 32 rear and 40DCOE 151 front. Other info: it has a euro manifold and "performance cams" (Centerline, I think).

These carbs are very different specs based on info found online (assuming nobody has messed with the various jets, etc). Even though I'm new to Webers it is clear this is not a good combo. It does not run well.

My question is which version (32 or 151) to find and make a matching set. Not sure if one is better than the other.
 

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These carbs are very different specs based on info found online (assuming nobody has messed with the various jets, etc).
I'd say you're making a big assumption to think that these carburetors' jetting hasn't been changed over the past 40+- years. Especially given the other modifications made by your cars' PO. Noting the sizes of both carburetors' jets, venturis, air correctors, etc. is the first thing you should do.

My question is which version (32 or 151) to find and make a matching set. Not sure if one is better than the other.
Neither is inherently "better". But sure, you want two carbs jetted the same and with the same progression hole patterns.
 
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I'd say you're making a big assumption to think that these carburetors' jetting hasn't been changed over the past 40+- years. Especially given the other modifications made by your cars' PO. Noting the sizes of both carburetors' jets, venturis, air correctors, etc. is the first thing you should do.
Agree. This car has passed through many hands. Will have to take them appart to be certain.

The 151 venturi is 30mm and the 32 is 32mm. I thought the venturis were not modifiable (i.e. part of the body itself).


Neither is inherently "better". But sure, you want two carbs jetted the same and with the same progression hole patterns.
I guess what I'm tangentially asking is if a 30mm or 32mm venturi is the way to go.
 

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40DCOE32 was the carb for a 1750 engine. 40DCOE151 is the spec number of new production DCOEs, made in Spain for the past 30 years, with plastic float and many changes since the DCOE32 was made.

The DCOE32 had 32 mm venturis (coincidence); they were often used with minimal changes on 2000s. A 30 mm venturi is rather small for a 2000.

Ideally you should get a second DCOE32; if you can't find one a pair of DCOE151s is not a bad choice.

UNLESS
the second carb is a DCOE32 with a 151 cover. Compare both carb bodies for visual differences.
 

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Do they have different floats?
Typo 32 will have the older round brass floats and Typo 151 will have angular nylon ones.
Typo 151's turn up on ebay periodically, both Italian made and Spanish made.
Ebay is buyer beware as we all know.
The tops are easy to swap out and carbs may be picked over for parts or have problems we can't see.
Here's an Italian 151:
 

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I thought the venturis were not modifiable (i.e. part of the body itself).
Nope, venturis just slip in and out.

I guess what I'm tangentially asking is if a 30mm or 32mm venturi is the way to go.
For a 2L engine, you want a 32 mm venturi. But any 40 mm DCOE will accept a 32 mm (or a 30 mm or a 34 mm) venturi.
 

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While the older Italian Weber’s have that “thang” about them, the later 151’s have some tuning pluses.

Keith Franck has recently announced that he’s freezing his VP tube designs, and working on the technical paper. I used an early design of his to replace the F16’s in my 2300. With no further dyno work, both the mid range torque and fuel economy improved.

It is probable that you can use a larger than traditional Venturi with his tubes. Increased upper end torque may not be what your seeking, but if you’re facing a total reset, why not?
 

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Keith Franck has recently announced that he’s freezing his VP tube designs, and working on the technical paper.
Don:

You have written about Keith Franck's work before and I have read some other references to his work. I look forward to his technical paper (where would it be published?). I see parts called "VP Main Circuit Tubes" on his webstore ( Webstore items for seller: DCOE_Tuner ) and you just made a reference to his "VP tube designs". Are Franck's "VP tubes" replacements for what Weber called "emulsion tubes"?
 

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They are.
 

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When it comes to Keith F, things can seem..... complicated. In a mad scientist sort of way.

I don’t believe anyone knows when or where his paper will be published.

As I understand the current situation....

Keith has discarded the idea of emulsifying fuel as part of the metering process.
He has currently devised three “VP” tubes that cover different ratios of cylinder volume to Venturi size.
A VP tube, of the desired size, fits where the emulsion tubes used to go.
He also has a range of adjustable idle jets that can deal with various conditions.
Although you continue to use the original style main jets and air corrector jets, he calls them “wet” and “dry” jets, and they do, indeed, perform different functions than before.

Until/unless he boils it all down in a future concise and readable paper, you contact him and describe the conditions in your engine, and he gets you started.
 

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Discussion Starter #11
Thanks everyone for the replies.

Learning lots of new things. Now for the dangerous part... going into the garage and applying them. :)
 
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