This has been a topic that has really hit the market within the last 5 years. So many products are introduced into the market that are not genuine. Does this mean its crap? The answer is not always.
Think about it, if you change your own oil in your car, the chances are that you are not using genuine products. You are more than likely using an oil filter produced by Ryco and Oil that is not OEM specifications. But does this stop you from using it in your car because it’s non-genuine? No. And we are talking about a product that can make or break an engine.
Same goes with products produced in China. Let’s face it, majority of products manufactured today are from China, Thailand, Taiwan etc. Just because it’s manufactured in China, doesn’t mean it’s always a DOA product. Chances are you are probably reading this on your Apple iPhone that is 50% made in China, or Computer Screen made by Samsung- with components made in China.
The meaning of all of this is Quality Control and Major Corporations. If it has a brand name on its product, the company will back it 100% to keep the brand name alive and un-tainted. If it does not have a brand name on the product, it means we do not know who has manufactured the product- therefore, it’s a product that does not have to be backed up when things go wrong.
Back to carburettors, we see the same amount of individual faults between Genuine Weber and FAJS carburettors. This is why before we sell you a Carburettor, we dis-assemble the carburettor to inspect the internals, checking float levels and that all moving parts are free from bind and smooth. We also back our products with a 12 Month Manufacturer’s Warranty. This gives you peace of mind when purchasing your product if something were to go wrong, as we have our name to maintain with our products.
You have driven your car and you are smelling fuely-rich smell. The carburettor must be running rich so you need to reduce the main jet size. This is generally incorrect and we need to ascertain the right areas of tuning before we start making the mixtures lean.
If you have purchased one of our Conversion kits, please note that we have Dyno-Jetted an average figure with a gas analyzer of the Factory Lean Mixture Specifications. Manufacturers made their motors run lean to meet emission regulations. We have matched those figures to be similar with our upgrade carburettors.
We need to identify the issue of the motor running rich. The following are examples of what can cause a ‘Rich Sensation’ that we need to diagnose. Before any professional tuner goes to tune a car, they need to eliminate any faults prior to a tune. This prevents any false tunes that can cause headaches down the track.
- Is the carburettor flooding? A Carburettor flood is a common misconception when it comes to a car running rich. It may only be partial but it’s enough of un-metered fuel that can cause a lot of headaches and mis-diagnosis. Check Float Levels and if there is contamination on the needle and Seat. Also excess fuel pressure going into the carburettor will cause a flood. Each needle and seat assemblies are rated at different pressures. (E.g. DCOE’s will only run at 3psi Max)
- Ignition - Ignition plays a huge part in how a car runs, and is generally what is causing or contributing to faults with the cars we get in our workshop. At times, we get sent cars to us claiming to be carburettor problems, which turns out to be faulty ignition systems and we never touch the carb itself. Things to look for:
- Weak Spark - If there is not enough spark in the cylinder to burn all the fuel, it will exit out as black smoke and give you that rich smell. Check spark plug condition, that there is no oil on the plug or that the plug is stressed. Also low voltage to the coil can cause a weak spark. You do not need an expensive coil unless you are using your vehicle for high-rev motorsport and the coil is to suit your application.
- Faulty or Un-tuned Points - Points or Contact Sets are also things people forget about. It is a dated piece of technology that requires a lot of maintenance in modern day times. If your points are damaged or the dwell angle is not set correctly and/or unstable, you will need to get this attended to before the final mixture tune. See Points vs. Electronic for more information regarding Points distributors.
- Timing - Not a usual area to create a rich example however, if your timing is heavily out, it will cause your motor to run in-efficiently. Check that timing is at factory specifications or slightly higher- depending on application.
- Misfire - If your motor is misfiring; this will almost definitely produce a rich sensation and will need to be addressed prior to the final tune. Areas to look for are Spark Plugs, Coil, Ignition modules or Points, Condensers, Leads. See common ignition faults for more information on components.
- Powervalve - Generally something usually looked at when tuning Holley carburettors. If a powervalve is leaking, it is usually hard to tell without physically checking. If a powervalve is stuck open and allowing fuel to pass when not required, this will create a richer mixture. Particularly on modified motors- please check Manifold Vacuum in relation to your Powervalve. (E.G. Your carb is fitted with a 6.5” Powervalve but your motor is idling at 4” of Vacuum. Your powervalve will be constantly open. Consider a smaller Powervalve or Blank)
- Does The Car Idle? This will generally help ascertain the right area to look for. If your car does not idle, then it means that the main jet is not the area of concern right now. A typical reason for a car not to idle is flooding, poor ignition and poor idle mixtures.
- I’ve adjusted the Mixture Screws but it does not change - This is a common misconception where people adjust the Mixture Screw(s) thinking it will change the overall mixture. This is incorrect. The mixtures screws only control the mixtures at Idle. As soon as you touch the throttle, those screws are made redundant.
If we have eliminated all these faults, then you may need to start looking at calibration. It’s not always just a case of changing a main jet; you need to figure out which particular area is running rich. Majority of your driving maintaining speed (highway) is done on your Idle Jet. Give us a call or speak to a professional local tuning shop for more info.
You are driving your car and you put your foot down, but the car flat spots, surges and/or hesitates. There are a number of faults that can cause this before we finally move to calibration.
- Timing - If your timing is not set to factory specs, higher or not advancing the way it should, you will need to address this issue as it can definitely cause those symptoms to persist.
- Vacuum Advance - Check your Vacuum Advance Canister is working. It’s a simple process that does not require tools. As the vacuum advance is a rubber diaphragm device, it is prone to aging and the rubber diaphragm will perish after time. To check this, all you need to do is get the other end of the vacuum hose that is connected to your canister and suck on it whilst the car is idling. It should hold vacuum and it should bring the idle speed up. If you suck on it and doesn’t hold vacuum but the idle speed increases- it means that the diaphragm works but it is unreliable. And naturally if you suck on it and nothing happens, then it needs replacing. It’s a common part that gets overlooked a lot by mechanics. If you need a replacement unit, please give us a call as we sell these units.
- Low Float Level - An abnormally low float level can cause you to have flat spots or surge. Raising the level will generally help. 4x4 owners please note: We intentionally set your float levels lower than factory specs as this helps when you go off-road driving. If you are unsure of specs, please give us a call.
- Low Fuel Pressure - If your fuel pump is faulty and not keeping up with demand of what the carburettor wants, it will mean that there is less fuel in the bowl and cause it to run lean. We typically see this when we fit new carbs to Suzuki Sierra’s and Mitsubishi Pajero/Tritons. As their fuel pumps are a rubber diaphragm, it is prone to perishing with age. As the factory carburettors were a Vacuum Secondary Carburettor- meaning the carburettor controlled the secondary throat; If there was not enough fuel in the bowl, it would simply not open the secondary throat. Check fuel pressure by a gauge only- it is not accurate if you pull a hose off and run the pump. It could still be running at 0.5-2 psi which is not enough.
- Contamination - If you have contamination in your fuel bowl, it may have gone through the circuits and created a partial blockage, thus not allowing enough fuel to enter the motor. Strongly advise to run an in-line fuel filter before the carb and after the pump to prevent major contamination. Factory filters are only before the fuel pump and is not adequate if your pump or lines start to deteriorate. Please note: No filter will filter rust. Rust will break down to such a fine micron that it will pass the micron rating of any filter. A strong magnet is a good way to maintain rust in one location.
- Pump Jet - Check to make sure that your pump jet is working. Check this visually by looking down the throat of the carburettor and applying the throttle. You should see a sharp squirt of fuel. **SAFETY NOTE: ONLY DO THIS WITH THE MOTOR TURNED OFF IN CASE OF BACKFIRE!**
- Powervalve - Check to make sure that the powervalve is working. Its not a common thing that causes a flat spot as it would typically make the mixture rich if a powervalve were to stop working.
If we have eliminated all these faults, then you may need to start looking at calibration. It’s not always just a case of changing a main jet; you need to figure out which particular area is running lean. Majority of your driving maintaining speed (highway) is done on your Idle Jet. Give us a call or speak to a professional local tuning shop for more info.
A Weber 34 ADR is a carburettor based off the 34 ADM seen on XE-XF Ford Falcons. We have taken the carburettor and modified circuits so that it will run efficiently on all 4 cylinder motors 2L and above. It is not just a case of changing the jets down in size, but making sure that the overall calibration of the carburettor suits the 4 cylinders. This includes removing auxiliary en-richening devices that were put onto the carburettor. The Butterflies are 34mm in size however; the diameter of the throats is what matters as it’s the most restrictive part of the carburettor for the airflow.
The Primary side is 27mm and the Secondary side is 29mm. We also have created our own Mixture Screw design for these carbs. This gives the end-user full control over the idle mixtures with great refinement, meaning you can tune your idle mixtures with ease, particularly for those ‘hard-to-reach’ areas.
These carburettors are reconditioned and modified in our workshop, using the Genuine Italian Weber 34 ADMs. They come with a 12 month Warranty and is has been one of our top selling product that we produce for nearly 10 years now.
A Holley 330CFM is a design that we have come up with while still using genuine Holley products for all 6 cylinder motors- modified or standard. The design is based off a 350cfm #7448 Spec Holley but we have altered a lot of the calibration. A custom metering block is just the starting point alongside with different boosters. We fit annular boosters into the carburettor as this helps smaller motors draw fuel from the boosters at lower air speeds i.e. taking off from traffic lights. With 8 holes and a larger venturi, this allows the fuel to be pulled through almost instantly as soon as you take off, eliminating the common issues of flat spots that people experience when fitting 350 Holley’s onto 6 cylinder motors.
When people fit 350 Holley onto 6 cylinder motors, they generally have to run the mixture extremely rich to make the car drive-able at low rev driving. This is not the correct method of tuning as you are just patching over a fault and using an excessive amount of fuel. With our 330 Holley’s, it allows us to calibrate the carburettor to factory original lean specifications without sacrificing drivability.
Give us a call if you need more information.
The simple answer is no. We get this question a lot and we will answer the reasons why it stalls and what we do to prevent this.
A lot of people who have experienced stalling up hills are because they are fitting a standard 350 Holley. The fuel bowls that come with these carburettors are not designed for off-road use. They were only designed for street driving only with mild inclines. The design of the bowl uses what we call a Centre Pivot Float- This means that the float pivots from the centre of the bowl in an up/down motion. This is why when we go up and down hills, the float will either be too high or too low and it will either starve the engine of fuel as the Needle & Seat will be constantly closed; or it will flood the engine as the Needle & Seat is constantly open.
With our Holley Conversion Kits for the 4x4 variants, we fit a side pivot bowl. The reason for this is that if/when you go up and down hills, the float is not interrupted. This is because the float pivots from the side rather than the centre. We set the fuel bowls so that it has the same, if not better “Spill Point” as what your factory carb will have. There is no loss of power or economy with using a different fuel bowl, other than the fact that it works to its advantage off road.
The reason why they don’t use Side Pivot Bowls on street cars is because street cars are designed to corner. So the Side Pivot Float would work as a dis-advantage around long corners. Similar to why we don’t use Centre Pivot Floats for inclines.
The factory carburettor has an inclination spill point at 32 degrees. They are non-adjustable. Now that they are getting old and most are using aftermarket parts, we are finding most will spill over at 28 degrees. Holley carburettors are adjustable and have optional floats, bowls and needle/seats. Our standard conversion kit is set-up for the original factory spec of 32 degrees. Some of our customers use our kits for extreme off road race, and hill climbs. With these, we have set-up their cars for up to 55 DEGREES!
Warning: Holley makes carburettors for street-race-rally-marine-truck and off-road. The correct off-road carb and options will do the job.
NOTE: Extreme 4X4, or competition use will require extra modifications, to be done on-car. Virtually impossible with the factory carburettor. Our 4X4 carburettors are successfully competing in extreme off-road events. Please contact our workshop if interested.
Some issues we see with carburettor fitments are the carburettor is facing the wrong way! There is a right and wrong way when fitting a carburettor. Generally, if a carburettor has a fuel bowl to one side of the carb, it needs to be fitted with the Fuel Bowl facing the Front of the Vehicle. This is because when we take off, the angle of the car tilts back. If the carb is fitted back to front, we will draw the fuel away from the main jets.
Easiest way to physically explain this is get a Glass or Bottle of water that you can see. Now tilt this back and forward. Notice that the physical level of the fluid stays flat but the item itself moves? The same principal applies with fuel.
If you have a carburettor where the fuel bowl is in the centre of the carb, then this rule does not apply as the fuel is drawn from the centre of the bowl.
This is a topic that is a hard question to accurately answer. The general term is no- and this depends on your application and carb of choice.
If you are purchasing one of our Replacement Carburettor Conversion kits, we pre-jet the carbs to roughly suit the Factory Specifications. We also need to remember that fuel consumption has a lot to do with added weight to the car (i.e. Bullbars, Wheels etc) and driver attitude. With the Replacement carbs, they all use a mechanical secondary throat. Most factory carbs were vacuum operated secondaries which mean that you only have control of the Primary Throat, the carb does the rest. However, the replacement carbs have mechanical so you have full control of the throttle.
With your newfound power, we tend to need to adjust our driving styles to drive more economically. We like to understand true fuel consumption after 2 Tanks worth of fuel with similar driving styles. This is generally enough time to start to understand your fuel usage. A fuel gauge is not always the most accurate device as it’s just a float with old electrics that are generally out of calibration.
If you are purchasing a sports upgrade carburettor set, then you need to appreciate that you are now modifying your motor for sport use. Whilst we don’t want to see crazy figures, you will need to expect a somewhat higher consumption rate than what your factory carb would have produced.
Also remember, we can always re-tune the mixtures of your aftermarket carburettor. That’s one of the key features of upgrading. You would not be able to tune factory carbs because calibration parts are no longer made for them.
Yes, this will typically make a much noticeable power gain. We must view this in correct context though; a carburettor does not make ANY horsepower, your engine does. A restrictive carb (original) will hold back a lot of the acceleration and power your engine can already make. Fitting a bigger carb (Weber/Holley) will allow your engine to accelerate as hard as it can. Therefore, fitting a ‘TOO BIG’ carb will not go any faster, as your engine is already making max power. (Unless we modify or "work” the engine for more power). We have dyno tested and modified the carbs as the most optimum for a standard engine.
You do not need a "Modification Plate" or certificate to change a carburettor. The kit we sell is a "basic" installation and complies with our local rules. All states and territories make their own and change their own rules. The installation of the kit can be altered to comply with any regulation. If you are unsure, please check with your Local Transport Department/ Roadworthy Inspection Centre.
The answer is no. Our Weber/Holley carburettor conversion kits are legal through-out Australia, PROVIDED the installation meets the requirements of your transport authority (varies from state to state). The fitting instructions supplied with the kit are a basic installation, which will pass safety certificate standards of QLD. Please contact us if you intend to refit your emissions, we will supply the carb to suit. Our fitting team can guide you through any emission fitting Aus-wide. We have been asked to do this a total of 8 times in our 20 years.
The 350 2 barrel Holley was first made for 5lt type V8 engines back in the 1960s. Since the 60s it has been used in Australia for smaller engines and 6cyl cars, as that was all that was available. It had no real problems at higher RPM, but had a wide reputation for sloppy fuel feed and poor atomisation at lower RPM. The 330 Holley was developed specifically for smaller engines and 6cyl cars. It has the same main body and base, so it will fit up to any Holley application, and the entire calibration has been reworked: Annular booster venturis are fitted to greatly improve atomisation, metering block is custom calibrated in various areas and pump is reduced.
The result is a carb that is much smoother and easier to tune. The street version also has the aluminium bowl with the fuel level sight glass.
The 330 is not too small for any 6cyl engine, as these are fitted frequently to 5lt V8 engines. It has exactly the same size main body, throats, and base plate as the 350. If there was any difficulty tuning it properly, we can help the installer/tuner trouble-shoot the problem, most problems are found and fixed over the phone.
Out-of-the-box, the 330 is jetted and set-up for a factory standard engine, to run the original factory lean mixture. They can be easily re-tuned for any standard or modified engine. Feel free to Phone our tech help. (07) 5493 3788.
The advantages of upgrading your carburettor from the factory standard to a Weber/Holley are:
- A simple, easy to tune carburettor: Factory carburettors were never designed to be tuned other than tweaking Idle Mixtures- and at that, some carburettors even had that locked. Now that you have a car that’s on average 30 years old, motors change. They get worn, tired or rebuilt. It needs tuning for it to be efficient. An aftermarket carburettor is easy to tune and calibrating parts are readily available.
- Remove troublesome emission devices: In the early ‘80s, emission laws were becoming strict. So manufacturers had to come up with ways of reducing toxic gas output. Devices such as secondary bowl vents, deceleration valves, EGR Valves, Charcoal Canisters to name a few. These generally become faulty after time, some classified as a consumable and need replacing. But these parts are no longer available. Deceleration valves are generally faulty in the ‘Open’ Position, making the overall Mixtures lean. Same goes for Secondary Bowl Vents. EGR Valves are a rubber diaphragm that is generally perished after time. Charcoal Canisters were used for a very long time, even with EFI cars. They are usually all blocked up now and create more issues than do any good. For more info on Deceleration Valves, CLICK HERE
For more info on EGR Valves, CLICK HERE
For more info on Charcoal Canisters, CLICK HERE
- Replacement Parts: Replacement parts for Factory carburettors are becoming increasingly harder to find. If and when you do find them, they cost a lot of money. Fitting an aftermarket carburettor will allow you to find new parts easily enough because all parts are still being produced by their original manufacturer. Even for some models, lets say Subaru Brumby, rebuild kits are becoming hard to find. We do not use the available kits for this particular model because their Needle & Seats are not reliable.
- Future Servicing Costs: You need to weigh up on what it will cost on continual maintenance costs including the possibility of another rebuild as well as replacement parts and tuning. Aftermarket carbs are cheaper to service because of the parts situation. E.g. TB42 Factory Carb Overhaul: $459, Holley Carb Service: $269
- Carburettor Access: If you have contamination within your carb that is causing issues with flooding etc, or to access jets. It’s a case of a few screws and you have access to the fuel bowl. Factory carbs have a variety of Linkages, Pump Plungers, and Devices before you get to the bowl. And at that, the screws on Factory Japanese model carbs are impacted in which make it difficult to remove and you often strip screw heads.
- Modifications: Whilst we try to maintain that our kits are easy and simple to fit by supplying all the components you need to bolt on, sometimes this can’t be the case. Some models do require some light modifications to allow you to bolt on the kit. Naturally, factory carbs do not have this issue. If you are unsure on what models need some slight modifications, give us a call and we can assist you with this.
If you have a modified motor, we can generally pre-jet your carburettor. However, it’s always advised that you have your engine professionally tuned with the right equipment. This ensures that mixtures are true and not running too rich/lean. Often, this is also the cheaper method as we can only guess what your motor needs. If it needs another tune, you are up for another set of calibration parts.
We often hear the term ‘My Motor has just been rebuilt’. THIS IS NOT THE DECIDING FACTOR OF ANY TUNE! We have had numerous motors that have been ‘rebuilt’, but many times they have been poorly done- Some motors dying within 50km of driving.
For example, Valiant HEMI E49 Spec motors. We have 6 different tune results including different tuners for the same Motor specifications. This just proves that no 2 motors are identical. We may have an average Baseline Jetting from previous tunes but we always know that it is not the final tune- it is still strongly advised to have the mixtures checked.
We do not mind doing a Baseline jetting for your set, if you are choosing to do the tuning yourself, we can give you some pointers and supply you extra jets. It is still an inaccurate method of tuning as it takes a lot of self experience to know what to change with fine tuning but we also understand money does not grow on trees.
It’s always the tough question that we get asked frequently. There is no set answer. It all depends on application, how you wish to drive the vehicle and size of the motor. It is not completely set by engine capacity on its own; it also depends on how you wish to drive the vehicle and what types of driving you are doing (i.e. Hill Climbs). We need to ascertain where exactly peak power is needed. One size does not give "best performance".
Let’s use Weber DCOE Sidedrafts as an example:
The venturi in Weber rally carburettors can be changed to suit how you wish to tune the car: smaller venturi can increase throttle response for a crisper acceleration on tracks that require the engine revs to brake and increase frequently (short tracks with turns and corners) often used for street performance. Larger venturi can produce more torque at higher RPM for tracks that allow longer sustained high RPM use. This is part of the "art" of motorsport. You will start by checking what size is in yours now, and with test-driving, decide how you wish to tune your car.
For sports/race carburettors: Weber DCOE/DCOM and Dellorto DHLA:
The venturi (or choke, throat size) in all these sports designed carburettors are changeable to different sizes:
The venturi size range of the 40mm carbs is 24mm to 34mm.
The venturi size range of the 45mm carbs is 30mm to 40mm.
Changing the venturi size governs the total air flow, and total horse power potential to the engine. If your engine requires 30mm to 34mm venturi, then you can use either size carbs, as both carbs can fit that size.
If your engine requires a venturi size smaller than 30mm, you will buy the 40mm carbs.
If your engine requires a venturi size larger than 34mm, you will buy the 45mm carbs.
There is much confusion (and very loose advertising) around this question.
Choosing single or twin carbs: You will need to view from two perspectives: performance, and economy/emissions. Performance: Twin carbs will win every time (based on inline 4cly engine. IE: one throat per cylinder). This includes ALL aspects of performance; top end, bottom end, low revs, high revs etc.
Economy/emissions: This is not so simple. Emissions are easier to control with a single carb, as manifold vacuum is maintained higher more consistently. Fuel economy can be made the same with single and twins at any SET RPM (cruising speed, etc), as fuel mixtures can be tuned as rich or as lean with either set. With moving the throttle frequently and varying loads (around town and stop-start driving), the twins will use more fuel and more emissions.
If choosing to use a single sidedraft carburetor, what manifold to use: Here, the “cross-over” design will produce more torque than the straight runner type at lower RPM (the same as V8 engines using dual-plane manifolds for lower RPM use). The straight runner types will produce better HP at top RPM, with some tuning needed to find optimum runner length (this is where ram tubes can help)
Do not now assume that the single “cross-over” manifold will produce more torque than the twin carb set, it will not.
What size carbs to use: Regardless of single or twin set-up, the size carburetor will depend on the venturi size chosen. The 40mm carburetor has venturi sizes 24mm to 36mm (although the 36mm size will have the carb run “sloppy” and should only be used in high RPM motorsport). The 45mm carburetor has venturi sizes 32mm to 40mm (again, the 40mm venturi will run “sloppy”). So if choosing a 34mm venturi, there will be little difference at all if using a 40mm or 45mm carburetor.
Some consideration should be taken for what diameter runner and head port, to keep the air speed consistent after the carb. Smaller ports will use the 40mm carb, larger will use the 45mm carb.
If the runner is splitting one throat into two cylinders (IE: single carb manifold), the venturi and carb chosen is typically bigger to maintain top end.
With all this “theory” out of the way, keep in mind practical use: Single carbs are mainly chosen because the end result is cheaper, easier to tune and maintain, and provides “enough” power increase for their everyday driving.
Twin carbs are best, when only the best will do.
Once carb type and size, as well as venturi size, is chosen, then a suitable base-line jetting can be advised as the jetting is worked off the venturi size.
When we use a sidedraft carburettor, or ‘throat per cylinder’ carburettor setup, there is generally not enough air speed to generate enough vacuum to completely pull the Vacuum Advance Diaphragm. As a Vacuum Advance is designed to run off Ported Vacuum and be used only when required, plumbing in a vacuum line to all cylinders under constant manifold vacuum will not work.
When you change over to an aftermarket sports carburettor, you should get your distributor’s timing curves re-calibrated. As the engine setup has changed quite severely, and that you are no longer using a vacuum advance, it is strongly advised that you get your distributor re-curved to get the maximum power and efficiency out of your motor.