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The 45s are equivalent to the 48 IDF Weber's, and if you're looking for a pair I will be posting a rebuilt set 45 dellortos here probably within the next month complete ready to go or just the carburetors.

@Jimmy V.-

People say that 40 Dels are the same as 44 IDF's and 45 Dels are equivalent to 48IDF's but that's because Del's from the factory usually have bigger venturis than the same size Webers.  Put the same size venturis in them and they'll flow close to the same and make similar power.

Last edited by ALB
@ALB posted:

@Jimmy V.-

People say that 40 Dels are the same as 44 IDF's and 45 Dels are equivalent to 48IDF's but that's because Del's from the factory usually have bigger venturis than the same size Webers.  Put the same size venturis in them and they'll flow close to the same and make similar power.

That is partially true, the dellortos to come with bigger venturies to the same size as the Weber IDF carburetors and if you match that Venturi size to a dellorto it will flow close to the same but the dellorto will still flow more due to the fact of the casting of the upper aux venturie is less restrictive of air flow than the weber as is the dellorto throttle shaft.

@Rick drla specialist-  I have asked this question before on other forums as I am not a believer that the Dellorto is some new whizz-bang revolutionary concept, but a slightly better version of an already proven and capable design.  I've looked but never seen any direct flow bench comparisons (same flow bench, same day) and no one (that I know of or read about) has ever tested them back to back on either the dyno or race track, so I'm led to believe that the flow improvement (and hp increase) is not big enough to be felt by most enthusiasts on the street.  Between my (years and years and years ago) dabbling at a little bit of bracket racing and riding in friends VW's with similarly equipped but Dellorto'd engines I didn't see enough to make me convert and sell my fairly large collection of Weber jets and emulsion tubes.    

The exception to all this is some (early?) versions of the 40 IDF- the carb tops are machined such that they will only accept 32 mm venturis, whereas later versions and all 40 mm Dellortos will take 34's.  I am of the understanding that those earlier carbs can be machined to the later spec and use the bigger vents.

So if you are of the first camp (the Del is a whizz-bang revolution) then we'll just have to agree to disagree.  But that's ok- it makes life interesting...  Al

Last edited by ALB

Stock 40 IDF is 28mm. I put 34 vents(max size) in 40s on a 2109 and it really woke up the upper end without softening the low and mid-range.

44IDF stock is 36mm.

I believe 45DRLA have 38mm, but not 100% sure about that.

Like you Al, I'm not convinced of the supposed Dell superiority. Other than WOT high-rev racing or dragstrip usage, I'll submit nobody can tell the difference on the street. I can't take the Pepsi challenge anymore since I switched from carbs to EFI. But I don't think my 44IDFs left much if any performance on the table on my 2165cc type1.

Vents are available up to 34 for 40 IDF and 38 for 44 IDF. Every part is available for Webers new, today. That is a good enough reason for me to stay in the Weber camp.

Every part of the equation has to work together: carbs, intakes, heads, cam, rockers, exhaust, compression, and yes, even the trans ratios and vehicle weight. If everything isn't sized properly the resulting combo is meh.

Last edited by DannyP
@ALB posted:

@Rick drla specialist-  I have asked this question before on other forums as I am not a believer that the Dellorto is some new whizz-bang revolutionary concept, but a slightly better version of an already proven and capable design.  I've looked but never seen any direct flow bench comparisons (same flow bench, same day) and no one (that I know of or read about) has ever tested them back to back on either the dyno or race track, so I'm led to believe that the flow improvement (and hp increase) is not big enough to be felt by most enthusiasts on the street.  Between my (years and years and years ago) dabbling at a little bit of bracket racing and riding in friends VW's with similarly equipped but Dellorto'd engines I didn't see enough to make me convert and sell my fairly large collection of Weber jets and emulsion tubes.    

The exception to all this is some (early?) versions of the 40 IDF- the carb tops are machined such that they will only accept 32 mm venturis, whereas later versions and all 40 mm Dellortos will take 34's.  I am of the understanding that those earlier carbs can be machined to the later spec and use the bigger vents.

So if you are of the first camp (the Del is a whizz-bang revolution) then we'll just have to agree to disagree.  But that's ok- it makes life interesting...  Al

100% Agree

As Danny said, 40 IDF's (for VW's) came with 28mm venturis, and there has been 27, 30, 32 and 34's made for them.  I believe 44's came with 36's with 28, 30, 32, 34, 38 and 40 mm vents made for them.  I think 48 IDF's came with 40's and 36, 38, 41 and 42 mm vents made.  As I've said before, there is a 36 IDF- I don't remember what they're off of (a Lancia maybe?).  There's usually a set or 2 for sale on Ebay, and I have no idea of the venturis it came with (24? 26? mm), and anything else would be custom machined to order.

Italian 48 IDA's have come with either 37 or 42(I think) mm vents from the factory with  36 to 46 mm sizes available from different sources.  There was a baby blue Cal Look Ghia Hot VW's cover car (1977?) with 32 mm IDA vents which the owner had machined up to make the 1600 in the car more streetable.  This, of course, was a time when no self respecting Bug-In winner would run anything but IDA's.  The smaller venturis apparently helped, but didn't totally solve the car's drivability problems- the carbs were just much too big for the engine.

Dellortos- each carb has venturis a size or 2 bigger than it's Weber counterpart, and what's available for each, sorry but you'll have to look them up.  Al

PS- There are 46 IDA's (or are they IDM's?) that came on some later 4 cam (2 liter?) engines. They're pretty hard to find.  You'll find 3 barrel 40 and 46(I think?) IDA's on some of the earlier 911's.  And Weber also made a 50 IDF- the only thing I know about it is it was on some big English luxury car?

Last edited by ALB

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