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Weber Carb Kits. With so many options choosing the right Weber carburetor kit can be a daunting task. That's why we've put together the Weber Carb Buying Guide below to help you choose the right features and installation kit for your needs. These image links below will take you to our listings for the various kit sizes.
Air-Cooled VW Bug, Bus, Sand Rail & Dune Buggy Weber IDF Jetting Guide
Weber Jetting Chart. This Jetting Chart provides a base line starting point. Every engine responds differently, and final jetting changes are most often determined by the engine builder or tuner. Engine size, cam, cylinder heads, ignition system, compression ratio, exhaust system, type of fuel, the vehicle and type of driving are all key elements in final calibration. The selection of main gas and air correction jets is determined by venturi size. The venturi sizes listed below are the sizes supplied by Weber in new carburetors.
The use of larger venturi will increase airflow, and larger main gas jets than noted below will be required. Weber Carburetor Parts. IDF Idle Jets F-2 F-7 F Search site:.
Services Engines Support Sanitary ware kuwait Contact. IDA Idle Jets Emulsion Tubes. F-2 F-7 F Carburetor Flow Meters.This section is provided to help the tuner optimize the performance potential of their when equipped with Weber, Solex, Zenith or PMO triple throat carburetors.
Although the body of the following text will specifically address components as used in the Weber carburetors, all of the processes are applicable to these four types routinely used on Porsche engines.
Weber carburetors are instruments used to realize your engine's performance potential; where "performance potential" is your decision: to maximize fuel economy, to maximize engine torque for ease of driving in traffic or to maximize peak horsepower for high speed sporting purposes. While it is possible to achieve improvement in two of these criteria, it is not possible to simultaneously satisfy all three.
Engine performance is maximized through carburetor tuning by first determining your goals and then by conducting performance testing. By evaluating the results of your testing in light of your established goals and by utilizing the guidelines provided in this section you may then make educated changes in the jetting and other configurable components to achieve the best compromise for your driving style.
Performance testing is required to determine the best selection and configuration of these components. The effort to understand the interactions of the different fuel delivery systems in the carburetor, conduct performance tests, evaluate the results and repeat the test with changed components is time consuming but the task is well worth the effort! If the jetting is rich then surplus fuel will wash the oil from your cylinder walls, dilute your engine oil and create carbon deposits on your valves.
On the other hand, a lean fuel mixture will cause the engine to run excessively hot causing detonation and eventually result in burned valves or holed pistons. Either rich or lean fuel mixtures will affect the engine's potential for performance and will negatively affect reliability, performance and service life.
However, carburetors do not have the flexibility in tuning like EFI systems provide; compromises may be necessary to insure you maintain adequate mixture strength at peak torque as an example and as a result, accept a non-optimum and non-damaging mixture during other operational ranges.
The primary feature of Weber carburetors is their adaptability. Different engines have different demands for air flow to fully realize their performance potential: small engines need less air flow CFM or cubic feet per minute of intake air flow while larger engines need more CFM and high performance engines require more CFM than a lower performance engine of the same displacement.
Webers are designed to use a common throttle body and by selection of different main venturi choke they may be used to provide for these different engine demands. However, optimization of the throttle body size is required to maximize the performance potential and efficiency of operation of any particular engine.
See Throttle body and main venturi sizing for more information regarding this topic. The ability to tailor the carburetor to best fit the demands of the engine assures optimum performance whether it is for street or performance applications.
However, this tune-ability comes with the obligation of the user to perform the adjustments correctly or suffer the results.
You engine, when equipped with two triple-throat Weber carburetors essentially has six single-throat carburetors but unless they all work together they will work against each other. Along with multiple tuning features comes the opportunity to get them all wrong. Any random adjustment may easily lead to a series of missteps that will ultimately necessitate a careful tuning effort to recover acceptable performance.
Idle jets supply fuel from idle to around RPM. Main jets supply fuel from RPM on. If your car has a bog or hesitation note where in the rev range it happens.
Air-cooled VWs in general like running richer than leaner. These engines experience higher head temperatures than many vehicles and more fuel leads to cooler running. Many carburetor related stumbles can be traced back to a lean condition in the rev range.
However please note that too much fuel can cause engine wear due to thinned oil. If your spark plugs are black and fouled or you see lots of black smoke coming from your exhaust after installing new jets you are probably too rich.
Air correction jets work the opposite of fuel jets. The larger the air correction jet the more air it lets into your air-fuel mixture. This will lean out the mixture. The larger the fuel jet the more fuel it lets in, which will richen the mixture. You can look at your spark plugs to get clues on how your engine is running. Light grey plugs or a plug with a melted electrode typically indicate hot running lean conditions. A dark sooty plug usually indicates a rich condition.
A wideband oxygen sensor is a great way to measure your VW bug or sand rail engine's air fuel mixture. Often these are installed during engine dyno sessions or for performance applications.A good deal of mystique surrounds Webers, specifically Weber jetting and tuning. However Weber DCO series carbs are not as complicated as you might imagine, and whereas there is no substitute for a good rolling road session to tune them, there is much you can do to tune them yourself, by selecting the correct choke sizes and initial jet settings according to a fairly simple set of rules.
This should get the engine running to a reasonable standard in preparation for the rolling road. When selecting Webers, the most commonly asked question is "Should I have 40s or 45s" coupled with "Surely the 45s will give more power".
This shows a basic misunderstanding of the construction and principles of operation of the DCO series. It is not the barrel size 40 or 45 which determines the airflow and therefore potential horsepower; it is the size of the main venturi or choke. Selection of the correct main venturi size is the first step in selecting the carburettor. It is easy to make the assumption that biggest is best when selecting a main venturi size, but the purpose of the main venturi is to increase the vacuum acting on the main jet in order to draw in and effectively atomise the fuel mixture.
The smaller the main venturi, the more effective this action is, but a smaller venturi will inhibit flow. A large venturi may give more power right at the top end of the power band, but will give this at the expense of lower RPM tractability.
The MG Experience
Only a circuit racer will benefit from this sort of compromise, on a road car, driveability is much more important. It is much more important therefore to select the main venturi for best driveability, once the venturi size has been selected, then the appropriate carburettor size can be arrived at. Below is a chart that will allow the correct selection of main venturi size for engines given the engines capacity and the RPM at which peak power is realistically expected to be achieved, for road engines peak power is usually between anddepending on the cam selection.
Carburettor Barrel size calculation. If you have bought your Webers second-hand, it is important to understand that it is unlikely that they will be 'ready jetted'. However if you do not want the expense of changing the main venturis, you will still need to know their size, this is normally embossed on the venturi itself, so look carefully down through the main barrel of the carb from the air cleaner side.
Diagram of Main Jet assembly. A useful formula for the calculation of main jet size when the main venturi size is known is to multiply the main venturi size by 4.
This will give a starting point for the main jet size which should be 'safe', again as a starting point the emulsion tubes can be selected from the table shown below, although for Pinto F9 or F16 will generally be OK. If your carbs are already equipped with these, then that will save you some money. Air corrector jet initial settings should be around 50 higher than the main jet.
Using these formulae, a venturi size of 36 mm will require a main jet of and an air corrector of around Emulsion tube Selection. Below is a table showing suggested emulsion tube type, for a given single cylinder capacity. Using the above formulae, the ideal settings for a cc Pinto with power peaking at RPM degree cam or above are as follows.
The cc Pinto in just on the cusp of change for emulsion tube type between F16 and F2if you already have F16 tubes, use them it is not worth the expense of change, they will just cause the main circuit to start marginally earlier. Diagram of Idle Jet Assembly. Idle jets cause a lot of confusion; although their name suggests that they govern the idle mixture, this is incorrect. It is true that the fuel consumed at idle is drawn through the idle jet, but the idle mixture is metered not by these jets, but by the idle volume screws mounted on top of each barrel.
The idle jets control the critical off-idle progression between closed throttle and the main jet circuit, it is this part throttle operation which is so important to smooth progression between closed throttle and acceleration and for part throttle driving. If this circuit is too weak then the engine will stutter or nosedive when opening the throttle, too rich and the engine will hunt and surge especially when hot. Below is a chart showing approximate idle jet sizes for given engine sizes, this assumes one carb barrel per inlet port E.
Establishing the correct idle jet for a given engine is not easy but usually an approximation will make the car acceptably driveable. If the progression is weak then the engine will nosedive when moving the accelerator from smaller to larger throttle openings. If this does not richen the progression sufficiently then the next jet size up, with the same air bleed should be tried. Below is a small chart showing the most commonly used air size designations, running from weak to rich. Generally speaking start your selection with an F9 air bleed.
This is the process we use to tune a car when it is in our shop. I have over 25 years experience tuning these carbs and there is no magic to it. It is just a step by step process that once you get the hang of it you will be able to make your carbs work right every time. It involves more than just Jetting the carbs and in fact that step is the easiest Following these steps and rules will also make it much easier when you are purchasing jets for your carb The 2 books listed at the bottom of this page are invaluable tools for learning all the basics of your carbs and the various metered tuning pieces that are used in them.
It is well worth the small investement in money and time to buy and read these books to help you better understand the carbs you spent all that money on. I am not going to explain everything about these carbs. These 2 volumes are the backyard mechanics guide to the basics you need to know to make your carbs run right Click Here to go Weber Carb home Page.
Step If you are having a problem with how the engine runs Poor idle quality, stalling, etc then this is the first thing to do. This is particulary true of new installations where you just purchased and installed a conversion kit and you are having problems. You have to remember that most Weber conversions have been around for many years and have been installed on hundreds of cars and trucks.
They work. The likelyhood of having a defective carb out of the box is about like being hit by lightning. If you are having a problem on a new install it is most likely this problem or one of the steps below See the Vacuum leak tech page for this info.
IMPORTANT TECHNICAL ARTICLE....Jetting and Tuning Weber Carbs.
This is the 1 problem with any Weber carb conversion. So not clean them Start fresh. This will give you a good reading of fuel mixture and enable you to make a good judgement of what you need to do.It is important to follow all linkage and lever installation instructions.
The number one and two reasons for tuning errors are improper linkage installations and over tightened linkage nut, causing a binding in linkage assembly.
Do not depend on the factory delivered settings. Check them before the carb is installed. All settings are done with choke disengaged or warmed up so that the choke is fully opened and disengaged. This is done on automatic choke carburetors by first opening the choke butterfly by hand and inserting a wood block or wedge of some kind to hold open while the linkage is cycled linkage operated through its full movement to clear the choke cam.
You will hear a metallic click as the cam is released. You can check the fast Idle screw under the choke assembly to confirm that it is not in contact with the choke fast idle cam.
Set the Idle stop screw speed screw see fig 1 by backing out the Idle speed screw until it is not in contact with the throttle stop lever. Cycle the linkage again to be sure that the linkage comes to close without any assistance. Set the mixture screw see Fig 1 by first screwing in until the screw stops, bottoms out. Back out the screw 2 full turns. Start the engine, the engine will run very slowly more like a tractor.
As long as the engine stays running idle speed is not important at this point. The first thing to do is not set up the idle speed, but to set the idle mixture screw to lean best idle setting. The engine should pick up speed and begin to smooth out.
Use your ear, not a scope or tuning instruments at this point. You want to tune the engine by sound. Adjust to best, fastest and smoothest running point.
Now that the mixture screw is at its best running location, you can adjust the idle speed the screw. Check and set idle to your driving preference.
Put the car in gear and apply slight load, AC on and set the Idle as you like it. Recheck timing and vacuum hook ups. Recheck mixture screw to lean best idle again.This article was complied from numerous articles and resources found on the internet, as well as our own experiences. The purpose of this guide is to cover the basics things you'll need to know to make your Weber carburetor run properly. This is accomplished by setting the adjustments properly, and by re-jetting the carb so it meets the requirements of your specific engine.
It's really pretty simple and not nearly as intimidating as you might think. A deposit will be required, which is refundable when the kit is returned in good condition minus the cost of any parts that are used, missing, or damaged.
For those that can't you need to learn how to read spark plugs, as this will get the job done. This is the reason that the Weber should give an improvement in fuel economy over most factory carbs, along with significant performance gains. If your engine isn't running at it's peak potential, you may need to make a few adjustments to the carb.
However there's a few things you should do before you start tearing into the carb. You also need to make sure your ignition system is working properly, that the distributor was designed to work with a Weber carb such as a Durasprk or DUIand that it is capable of supplying an adequate spark to burn the extra fuel. Stock points style distributors are not up to the task, and need to be replace with a electronic distributor, an ignition box, and a hotter coil. Good plug wires are also required.
Vacuum Leaks Let's back up just a bit Vacuum leaks are the 1 problem with carb swaps and conversions. This is particularly true of newer installs, as the chances of having a defective carb out of the box, are about the same as being struck by lightning. The first thing to check is the gaskets between the manifold, the adaptor, and the carb.
In most cases we recommend using Silicone Gasket Maker between the manifold and the carb adaptor, since the adaptor never needs to be removed once it has been installed. This will greatly reduce the chances of a vacuum leak at that point. Next, we highly recommend a gasket between the adaptor and carb, so the carb can be easily removed for maintenance and tunning whenever needed.
Make sure you use a new gasket, not an old one that may leak. You cannot tune carbs that do not have adequate and proper fuel delivery, as it is critical to the proper performance of any Weber carb.
Mechanical pumps very rarely do this. They pulse fuel instead of giving a smooth even delivery, and the amount of fuel varies with engine RPM. A good electric fuel pump will provide the best performance and a stable supply of fuel for tuning your Weber carb. It should be noted that Weber carbs work best at 4 psi, not 2 psi, like many of the older books state.Synchronize Dual Carbs on VW Type 1 Air-cooled Motor
You also need a pump that will supply an adequate volume of fuel, not just pressure, as volume is what's needed to keep the float bowl full under periods of high demand. As such, we recommend a high volume, low pressure pump, that delivers GPH at psi.
The Carterwhich is a rotary pump, is an excellent choice.