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I am trying to piece together where we stand on Weber conversions for the 2600. Sort of a summary of what has been most successful and what course to take in attempting to convert from the Solex ph44s.

Without expecting a book on the topic, can someone take a crack at a recommendation on how to proceed, what to acquire, and best practices?
 

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Hi,

My experience and personal choices:
Conservation of the intake manifold by separating the ducts. I used specific resin (high T ° and resistance to gasoline) which I molded around cores to guarantee uniform conduits.
Here pictures on my 2000 :

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Use of Weber 40 with the same setting as typo 105-1750:
  • Buse : 33 mm
  • Gicleur principal carburant : 120
  • Gicleur Air : 150
  • Tube d'émulsion : F 16
  • Ralenti : 50 F 9
  • Pointeau : 200
  • Fond de cuve : 55
Result on my previous 2600T. The engine was fantatic !!!

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Serge, could you please post a product shot of (or link to) the resin you used?
 

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Curious. Has anybody tried the Solex carbs after separating the inlet manifold ports?

Pete
 

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Pete, the Solex PHH carbs do not allow for that because one half of the carb feeds 2 cylinders, except for wide-open-throttle.
 

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I'm not quite sure I get what you have done to divid the runners. What is the black material? Is it some sort of foam type of material or some type of material that you melt it once it's in place in the runners or do you pour resin around the black material and then remove or dissolve the black material? Please give a detailed explanation of the materials and the process you have used to form individual runners. Thank you!
 

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Sorry, I'm going too fast ...
The manifold of the 2000 has ducts whose inlet diameter (at the carburetor outlet) is larger than the outlet diameter (at the cylinder head inlet). During the sealing operation, it is important to obtain a regular conduit.
I took a simple heating tube insulator (it is very common in France) :

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I chose it with the right outside diameter (I don't remember exactly but on the 2000 it must be 45 mm). I reduced the tube so that it has the right diameter at the outlet of the collector (pictures 1 and 2 above).
A little silicon grease to take it in. I pierced the collector at the top.
Here a picture of the tube in one of the conduits.
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I filled the space between 2 tubes with my resin.

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After cooking, the release is done without problem, by pulling (sometimes by tearing) the tubes.
Finally I applied a paint that I use for the interior of the engine blocks, but it is not necessary. The way to the valve is very clean.

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Don would tell you that it is better to use the OKP manifold for the 2000s because the conduits are linear (but that's another story). On the 2600 the conduits are less curved than on the 2000 and this technique makes it possible to have a very clean result with little effort and money.
If you don't want to do it by yourself, there is a specialist in France (Alfa Classics Motors) who machines the collector and fits a conical tube there.

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The Solex PHH44 carbs do not have the same plenum attachment pattern as Webers. Various people have made “gender menders” to attach the original plenum to Weber’s.

Actually, I do not know if the OKP manifold has more efficient ports than your modified manifold. The poster’s question was regarding the 2600 in any case.

As part a very general statement, curves in intake ports reduce efficiency, but other factors may dominate. A changing cross sectional area can pose problems as well, but correctly done one can created an accelerated flow that improves cylinder filling and swirl.

I read a study several years ago that determined that intake manifold walls should be a little rough, not smooth, as this helped avoid fuel drops forming on the walls.
 

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Very nice engine and engine bay

Pete
 

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Very nice engine and engine bay

Pete
Any discussion of Weber conversions would be incomplete without noting that a full reproduction Weber manifold is now available from Hasselgren Engineering in Berkeley, CA. Paul Hasselgren, who made his reputation building and tuning modern and vintage competition engines, used 3D scanning techniques to produce an exact copy of the original Alfa 2600 Weber manifold. See attached photos. The manifold performs like a Weber manifold should and is available for about 50% more than a "converted" Solex manifold.
 

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OK, 2600 owners. Time to quitchyerbitchin and do it right.
 

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Don, thanks for saying it like it is. It is long overdue. No more half a-sed crap that doesn't work properly for airflow like a correct Weber intake manifold does. For those of you who have 2600 Spyders worth a small fortune, it's hard to imagine that having a proper intake manifold isn't worth the cost that Hasselgren Engineering is asking for you to do it right. Noboby, and I mean nobody, has anything like it currently available. The manifold is work of art, for goodness sake. To finally have this available is a wonderful benefit for the Alfa community. I've got one coming for my 2600 Sprint and I can't waiting to move forward with my car.
 

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The price I paid is $3700 with everything on my manifold shown in the pictures except the thermostat, the Weber carburetors, the carburetor linkage and the "gender menders." The other fittings come with the manifold. I also ordered for an additional $600 the adaptors with rubber "o" rings to use instead of the rubber adaptors shown in the picture. I'm aware of the need for the rubber isolators for the carburetors but I'm fuel injecting my engine so I don't have to worry about vibration in the float bowls.
 

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This is certainly by far the best Weber manifold reproduction I've seen -- and, given the quality and difficulty of making it, it seems to come at a fair price.

However, something worth noting is that the ports of the intake runners appear to be substantially smaller than on the original Weber manifold (see pictures below).

Whether this is so for making this manifold a better match for 40 DCOE carbs (which very likely are better for road use than 45 DCOE), and/or to leave enough meat on the bone for porting and polishing, I don't know. It is also possible that the pictures above were taken during an early fitting where such work was not yet done (which would leave the question whether or not such work would be included in the price).

Either way, potential buyers should be aware that even manifolds in such great quality may not just be a simple bolt-on replacement, but may require additional work (e.g. porting) for adapting them to their specific setup and/or needs -- and there's nothing wrong with that.


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Beginning in about 74, I noticed that the 45DCOE9 was listed in the Weber factory catalogs as original fitment for the 2600 Alfa. "Huh", I thought. By the time I was selling Webers as part of my job with BAT/Geon, I'd also worked as the parts manager for an Alfa dealer that also sponsored the owners Alfa race car. The 45DCOE was generally considered appropriate only for very large capacity engines (at least on a per-cylinder basis). The 2600 has a per-cylinder volume very close to the 1750, and it was only when those were used as race engines that the 45 was brought into play. I'm using 45s on my 1959 2000 which has a 2300cc engine, itself having approximately 33% larger per-cylinder capacity than the 2600.

On the other hand, early 45's make no pretense about being economizing with fuel. The transition zone tends to run quite rich, avoiding flat spots. I ported my OKP manifold to match the 45s (they are intended for 40's), and things have been quite happy since the first start. I've done some adjusting, and am using a non-original E-tube from Keith Franck, but I've never had a hint of the transition bog that seems to bother 2600s with modified Solex manifolds, as well as some reports using a Weber manifold.

If these new manifolds are delivered with bores appropriate for 40s, I'd use them. Set each one up the same as for a Euro 1750, and betcha it works.
 
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