• How To Build & Power Tune Weber DCOE/SP & Dellorto DHLA

This is a brand new Weber DCOE & DCO/SP & Dellorto DHLA manual. It is the latest 3rd colour edition.


- New! Enlarged, revised and updated edition - complete with extra illustrations - of Veloce's best-selling SpeedPro title. 
- New information on Dellorto carburettors
- All you could want to know about the world's most famous and popular high-performance sidedraught carburetors. 
- Application formula gives the right set-up for YOUR car. 
- Covers all Weber DCOE, DCO/SP & Dellorto DHLA carburetors. 
- Strip & rebuild, tuning, jetting & choke sizes


The objective of this book is to provide understandable information that will allow anyone with reasonable mechanical knowledge and aptitude to successfully strip, rebuild and tune Weber and Dellorto sidedraft carburetors for optimum performance.

There is no need to put up with a modified engine fitted with these fantastic carburetors that coughs and splutters or consumes huge amounts of fuel. The information in this book will help you to quickly isolate particular problems and alter the carburetor/s to suit your engine's actual requirements.

This book contains no details of choke (as in cold start device) settings because in most cases choke is never used with these carburetors. Cold starting is usually preceded by a partial pump of the throttle pedal to activate the accelerator pumps and, once the engine has actually started, working the accelerator pedal to keep the engine going until it is able to idle. Chokes just don't seem to get used because it's so easy to use the excellent accelerator pump system fitted to these carburetors instead.

Webers and Dellortos are truly excellent carburetors to work with. Even in this day and age of high technology there still is a place for 'simple' carburetors that give high performance while basically being bolt-on items. Webers and Dellortos meet these requirements and their future is assured. One thing is for sure, on a cost-for-cost basis, Webers and Dellortos (especially if good second-hand carburetors are purchased) can give unrivalled value for money.

There is an old adage "what looks right is right" and this certainly applies to Webers and Dellortos. They always "look the part" on an engine because they are the part and, no matter what the engine size or type, they can be made to go as well as they look.

I hope that you find this book informative and a practical help in the quest to tune these carburetors to get the best possible performance from your car, allied to reasonable economy.

Weber DCOE versus Dellorto DHLA

Argument has raged for years about whether Weber or Dellorto carbs are better, however, no realistic comparison is possible unless all of the available adjustments have really been optimized on each carburetor type and on the same engine.

Fortunately both carburetors are so good it doesn't matter too much which manufacturer you choose and personal preference is as good a reason as any to buy one over the other. The main thing everyone needs to know is that you can buy either with absolute confidence in their performance. Both carburetors are able to be tuned equally well. There are no bad sidedraft Webers or Dellortos.

Nothing of any consequence interchanges between the two make of carburetor. The only thing common to both is that they will bolt on to the same intake manifold.

The design differences between the two carburetor makes show that their respective manufacturers have achieved the same objectives, but by different means. An example of this is the accelerator pump action. In both cases the engine receives an identical amount of fuel but one carburetor has a diaphragm and the other a plunger. The Dellorto exhibits what can be termed modern manufacturing techniques which modernize the original Weber carburetor concept to a small degree. The Weber was designed and built in the days prior to reliable fuel resistant plastics and originally had brass floats, for instance. The Weber is an all metal device designed around the materials of the time and it has remained basically unchanged since then.

The Weber was certainly the original and there is no question that the overall concept is brilliant. There is also no doubt that these facts have contributed to Weber having the best-known 'name' and performance image and the DCOE is likely to remain in this prime spot as Dellorto ceased production of the DHLA range in 1991. Second-hand prices are generally higher for Webers even though the new price of each was similar. There are literally thousands of both types of sidedraft carburetor scattered around the world and millions of tuning parts sitting in tool boxes and garage cupboards. These carburetors are going to be around for a very long time and continue to be fitted to a wide variety of engines.

The Dellorto company designed their carburetor with the view to improving the Weber formula and they have achieved this to a certain extent. The integral, plastic-caged fuel filter is well done and better than the soldered brass mesh tube of the original Weber or the plastic-caged filter alternative available these days from Weber (which often crushes the first time it is installed). The choke operation is certainly better on the Dellorto (same overall principle) from the standpoint of having a good shut off by way of the neoprene washer and the piston action that uncovers the holes for the fuel /air mixture to pass through (no fuel mixture leakage problems).

The Weber choke/fuel enrichment device can be troublesome when it gets a bit worn and can pass a huge amount of extra air/fuel mixture into the engine; in fact to such an extent that the engine may not even run. The problem being that, although the mechanism is in the off position, it only takes a bit of lever wear and a jammed starter valve (in the up position) and you have a very rich mixture. However, if the choke has never been used (most have not) this situation will not arise. The choke outlets can be blocked off permanently to preclude this happening. Note that if either of the starter valves found in a carburetor do not seal off they will allow fuel mixture to pass by.

The venturi choke and auxiliary venturi are held in position with a single taper point screw and lock nut on all Dellorto carburetors and this is an excellent retention method. The Weber uses a single taper point screw for each on 45s and 48s with a securing plate linking the two screws and bent tabs for a locking arrangement. The locking tabs must always be fitted to prevent the screws from winding out (they can be lockwired).

The DCOE 40s on the other hand have blade spring location on both the auxiliary venturi and the choke. Both are held in position by the trumpet and its two retaining clamps. On well used carburetors the trumpets can often be found to be rotating, even when the trumpet clamps are fully tightened. There are several reasons why this happens (none of them good) but the end result is that the carburetor body gets worn and even a new trumpet, choke and auxiliary venturi will not restore the situation although specially made trumpet clamps (stepped) will cure the problem.

The accelerator pump lever is not as compact on the Dellorto as the Weber's (which it is totally enclosed within the carburetor body). The Dellorto components could be damaged through lack of care but it is not usual for this to happen: in fact, both carburetors are pretty hardy units. The more modern style of the Dellorto's construction and methods it uses to duplicate the Weber principal of operation have been very successful overall. The differences between the carburetors mentioned here are all pretty minor in the overall scheme of things but worth noting to illustrate that both carburetors have strengths and weaknesses when compared to each other. Dellortos are a little bit easier to service. The Weber is more compact height-wise.

The method of tuning either carburetor is essentially the same. Unfortunately, in both cases, the axiom "bigger is better" seems to prevail but, in most instances, this is wrong and most engines that do not run well and prove to have carburetor problems have chokes that are too large, main jets that are too large, accelerator pump discharge jets that are too large or too much fuel pressure. It is difficult to understand why anybody would want to go to the time and trouble of fitting Webers or Dellortos and for the sake of a comparatively small amount of money put up with an uneconomical and poorly performing engine. This happens all the time and the carburetors are often blamed for it when, in fact, this is not possible as both carburetors are infinitely tunable to achieve perfection in all instances. It is the tuning of the carburetors that is the real problem.

The competition engine built professionally and on a big budget is run, tuned and tested by the particular concern doing the job. However, the majority of Weber and Dellorto users do not have the sophisticated equipment that a major tuning company will have, yet their car's engine still needs to be tuned correctly. In fact this is not such a big problem because the principles of Weber and Dellorto carburetors are logical and understandable so that, when sound tuning techniques are employed, both carbs can be tuned correctly with a minimum of equipment.

The average enthusiast will never have the same resources at their disposal as the professional but, with care and attention to detail, can get an engine tuned equally well. Of course, money can be saved if the right choice of components is made first time! All of the jet sizes given in this book are approximations because individual engines vary so much. If your engine is being rebuilt and you intend to use high revs, make sure it is built with the biggest permissible tolerance sizes on the piston to bore clearance and the main and big end bearing clearances (factory specifications, but largest sizes permissible). It is not possible to tune an engine that has some mechanical problem. Well-built engines respond perfectly to correctly tuned sidedrafts.

Note that Dellorto and Weber have both supplied their carburetors to car manufacturers as original equipment. There are some differences in these application specific carbs that can cause the second-hand price to be less, especially Dellortos. Compared to standard off-the-shelf Webers, carbs made for specific applications can feature idle mixture adjustment screws in towers, vacuum take-offs, or provision for them, on the right hand side of the carburetor body (when viewed from above), different auxiliary venturis for fitting to an air box (no trumpets) and a smaller float vent hole (or no float chamber vent hole) but the carburetor uses a vented jet inspection cover. None of these features affect the tuning of these carburetors but they usually sell for less second-hand. Some application specific Dellortos have pre-drilled holes in the carburetor body that control the air bleed for idle mixture adjustment, fuel mixture strength and progression mixture strength. These carburetors are perfect on the particular engine they were built for but usually prove untunable at idle, and just off idle, on anything else because of the lack of adjustment.

The advent of electronic fuel injection systems for production engines has not replaced the sidedraft Weber or Dellorto in the eyes of many because these systems have brought in an element of complication and expense. Overall, the performance of these injection systems (if correctly set-up) is unmatched by any carburetor but the difference between fuel injection and well tuned sidedraft can be very small.

The new parts situation often favors the Weber and they always seem to be available at reasonably short notice anywhere in the world and from many sources. This is not always the case with Dellorto parts. Dellorto sub-agents never seem to have any stock on hand. It seems to be a worldwide trend that Dellorto parts are a little bit harder to get unless the main agent is approached directly. All parts are available for either carburetor from your country's main agent and the agents have direct factory access for the purchase of spare parts. Parts are, in fact, not really hard to get for either make of carburetor, you just have to know where to go for them.

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How To Build & Power Tune Weber DCOE/SP & Dellorto DHLA

  • Brand: Weber
  • Product Code: WEBDEL
  • Availability: Out Of Stock
  • £26.00

  • Ex Tax: £26.00

Tags: Weber, Manula, Dellorto