Weber Carby Upgrade Instructions suit any 4 cyl carby motor.

Engine related articles specific to induction (carby, EFI etc.)
benwahn
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Post by benwahn »

I put a fully reconditioned weber on my gem. I took the choke off too. It did run rough to start with, and would flood at lights, in the maccas drive thru and in heavy traffic. I adjusted my idle mixture (cant remember how but it helped). It still ran a little rough so i went over my ignition system and replaced points , condenser , dizzy cap , leads , plugs and rotor button. Then i just timed it and it runs sweet as! Starts first hit every time at 5:30 am , never misses or floods. Theres extra fuel to be burnt so maybe thats why ppl are havin problems with backfiring etc.

hope this helps
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Buggzy
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Post by Buggzy »

Photo links fixed... !!
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andy_vlct
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Post by andy_vlct »

gday,

What would cold starts be like in near (and sometimes) 0 degree wether with this carb?

Would you need to use the webers choke or will this carb start alright in these conditions? how would you hook the choke up to the gemi?

Tassie is a b*tch :roll: lol
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Post by Buggzy »

well acutally dude was talking to a guy down calder park the other night and he had a 32/36 weber on with the choke and it wasnt hitting brake booster, and i asked how he done it and he said he made up a spacer under the engine mount to lift one side of engine up a fraction and that fixes problem, so u can run the choke and it will run sweet. Without choke start up on really cold mornings is a bit of a c*#t.. just gotta pump it before hand and then keep revs up for a couple of minutes untill it warms a bit.
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TURGEM
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Post by TURGEM »

webbers are quite a carby to tune they are so much better than say a 350 holley or upwards in tune wise in a weber there is about 4 different circuits that can be tuned seperately but the most important one is the idle circuit and idle mixture if this isnt setup correctly then the whole performance of engine will not be up to scratch. if you would like i got some special tuning info on webers in regards to 32/36 just if possible let me know and i can post it up step by step. but im new on here so i dont know the rules in regards to makin new thread. once i read the carb tuning was so much easier to understand and do. :lol:
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Post by Buggzy »

7URG3M wrote:webbers are quite a carby to tune they are so much better than say a 350 holley or upwards in tune wise in a weber there is about 4 different circuits that can be tuned seperately but the most important one is the idle circuit and idle mixture if this isnt setup correctly then the whole performance of engine will not be up to scratch. if you would like i got some special tuning info on webers in regards to 32/36 just if possible let me know and i can post it up step by step. but im new on here so i dont know the rules in regards to makin new thread. once i read the carb tuning was so much easier to understand and do. :lol:
you have PM.,..
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Post by TURGEM »

Jetting and Tuning Downdraft and Sidedraft Weber Carbs.
An Overview and Short Course: (This is currently a work in progress...I wanted to post what I had done so far..It will continue to grow as more time allows...Bookmark it and come back often and pass it along...)
Okay....This is going to be the Short Course in what you need to know to Tune and Jet your Weber Carbs successfully...This also applies to Mikuni, Solex, Etc....This is not specific info about specific cars or giving you magic jetting numbers. This is the process we use to tune a car when it is in our shop. I have over 8 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...This applies to a single 2 Barrel Downdraft 32/36 Carb or a set of Triple DCOE carbs or even a set of 4 Downdrafts on a V8 engine....

I am not going to explain everything about these carbs. The Weber Factory Tuning manual has all the good technical information already written. This is the backyard mechanics guide to the basics you need to know to make your carbs run right....
Step-1: If you are having a problem with how the engine runs...Poor idle quality, stalling, etc then this is the first thing to do. CHECK FOR VACUUM LEAKS ! 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 conversion 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. DO NOT OVERLOOK this as a problem...This is the #1 problem with any Weber carb conversion.
* Do a compression test..If the compression is off by more than 10% per hole you will have a really bad time tuning the carbs.
* Always start with a fresh set of Spark Plugs. 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.
* Set the Timing...Generally speaking you need a little more advance with a Weber than with the stock carb. A good place to start for most cars with Webers on pump gas is 12-14 Degrees advance at 1000 RPM idle and 36 Degrees total advance by 3000 RPM...This is not cast in stone and you need to make sure your car does not Detonate at these setting. If you get any detonation then you need to back off the timing...
Step-2: If you have a single carb you can skip this step...If you have multiple carbs then the 1st thing you need to do is make sure the carbs are Synchronized properly using a Correct Synch tool. This is CRITICAL to multiple carb performance...I don't care how good you think you are at synching a set of multiple carbs by ear (I'm very good and I'm not half as good as the tool is.) you are not close enough. The Synch tool will also alert you to other problems in the system like Bent throttle shafts, etc.... Linkage...This cannot be stressed too highly. Badly designed or Worn linkage is the #1 cause of problems with Multiple carb systems. More people have given up on Dual and Triple carb systems because of linkage than any other problems combined. If the carbs are not hooked together in a fashion that has no slop and allows minute adjustment between the carbs you are always going to have problems. Poor idle quality and "sticky high idle" problems are the most common symptom of this. A slight imbalance between the carbs at 1/3 throttle and up is not really noticeable to most people but a miniscule difference at idle will cause all sorts of problems. So in short...Get the carbs synched right FIRST. Repair or replace the linkage as needed to make them work together properly.
Step-3: Know what is in your carb NOW. Do not rely on a list on a website or a book that says what your carb might have come with. Actually remove the jets and chokes and check the sizes and WRITE THEM DOWN. Use this form to write it in so you know what you have. You cannot make jet decisions unless you kow what you are starting with...
Step-4: Make Sure your Ignition system is working properly. Remember...A Weber carb is always a performance upgrade and is designed to deliver more fuel and air and make more HP then the stock carb did. This means you need to have adequate spark to burn the extra fuel or you will have problems tuning and jetting your carbs. This is especially true of old Aussie cars and cars that have point type igntion systems. A lack of spark or weak spark will make it impossible to tune the carbs properly or to their maximum potential. This is especially true of all multiple carb installations. You cannot hang multiple carbs on any engine without an increase in spark output and even hope to burn the extra fuel being delivered. A good electronic Ignition system to replace points and the addition of an MSD unit and good coil and wires are the best way to go.

Step-5: Make sure that your Fuel Delivery is right....Once again, you cannot tune carbs that do not have adequate or proper fuel delivery.

Step-6: Okay...Now that you have everything else sorted out ( Right ? You did do all that other boring stuff didn't you ? ) you can actually start tuning the carbs...The good news is that you probably made the car run good enough by doing those other steps that there is not alot else to do..... If your car is still not running properly or you feel that you should have more power (Be realistic about that. A 4 cylinder 2.0 with a 32/36 is only going to make about 120-125 HP max so don't expect miracles.) then it is time to jet and tune the carb(s) You need to establish if you are running lean or rich. There is no way around this. There are a few easy ways to establish this and it is important to know otherwise you cannot get different jets to cure the problem. You can be running Rich at idle and Lean on the main circuit and Vice Versa...You need to do a plug check....Unless you have access to a 3 Gas or 4 Gas anaylzer or Smog Machine to do your tuning then reading the plugs is the next best thing..Another good option is to install a Halmeter AF30 Air Fuel Ratio Gauge to help you with tuning. It is fast and accurate and will take alot of the guesswork out of it. This is a particularly valuable tool for cars that get track use so that you make sure you do not lean out and put a hole in a piston...
You need to check your spark plugs to see if you running rich or lean. White plugs are lean and Black plugs are Rich. Ideally you want the ceramic part of the plug a nice Dark Tan to medium Brown color with a slightly darker ring right at the base of the threads of the plug. A new set of plugs may take a few minutes to get some color on it...
Idle Mixture and Fuel Mixture:
There are alot of theories about setting idle mixture adjustment on a Weber carb to determine Rich or Lean jetting....A Weber will run correctly with the mixture screws from 1/2 turn to 3 turns out...The late style DCOE carbs with the extra Air Bleed Screws on the top take 2.5 to 3 turns to operate correctly...So you cannot say that because it is 1/2 turn out that you need smaller jets....You need to find what is right for that particular engine...An engine with a strong vacuum signal will draw more fuel in with less turns of the screw than an engine with a weak vacuum signal will...This is the kind of thing that throws the "certain number of turns" theory out the window..
The Mixture screw and idle circuit is CRITICAL to the overall driveability of the car. It does not just control idle but the entire low speed running and part throttle transition. The mixture screw lets in an ALREADY MIXED volume of Fuel and Air to the engine. This is not an Air Screw. The more you open it the more mixed fuel and air enters the engine. Clockwise is Leaner and Counter-Clockwise is Richer.
The mixture screew is very easy to set whether it be a downdraft, sidedraft or multiple sidedrafts. Start with the screw or screws out 1.5 turns....Start the car and let it warm up. Set the Idle SPEED to approx 900-1000 RPM..Make sure multiple carbs are synchronized...Turn the mixture screws in until the idle starts to stumble and get rough...On a sidedraft with 2 screws do them each a little at a time....Then back them out until the best idle quality is acheived. This is a very simple operation...The car should idle well and small adjustments leaner (Turning them in) should make the idle drop off. Opening the screws more should make it a bit richer but it should still idle. Assuming you have no vacuum leaks this is a very simple process. If you cannot get a good adjustment on these screws and you have to open the idle speed screws quite a bit to get the engine to idle there is a good chance you have a Vacuum Leak and you need to fix it.
Specific Information on Mixture Screw Setting for:
32/36 DGV, DGEV Carbs. If you have to open the mixture screw more than 2 turns on a 32/36 DGV or 38 DGES your idle jets are too small...If you have to shut them below 1/2 turn they are too big....
38 DGES. If you have to open the mixture screw more than 2 turns on a 32/36 DGV or 38 DGES your idle jets are too small...If you have to shut them below 1/2 turn they are too big....Also the 38 DGES can be a little tricky because you are idling on both barrels at the same time. You have 2 mixture screws and they will not be set the same on most cars. This is because the plenum type manifold that they are on distributes fuel unevenly. By having 2 mixture screws you are delivering fuel from 2 places in the intake manifold. The Mixture screw closest to the engine will no doubt need to be in much farther than the outer mixture screw. This is Okay. I do not recommend Stagger jetting the idle circuit on a 38 DGES (In other words, do not use 2 different size idle jets even though you need to adjust the screws differently. This can cause part throttle dirveability issues.)
DCOE Series and IDF / IDA. On a DCOE or multiple DCOE's you should be between 3/4 turn and 1.5 turns out for all older model DCOE's (DCOE 2, 9, 18, etc.) and 2 1/4 to 3 turns out for late style DCOES (151 and 152 with air bleed screws under the white caps.)
Idle Jets and tuning the idle circuit: Very Simply..The bigger the number the richer the jet. A 50 Idle jet is a .5mm fuel hole. On the DCOE and IDA series carbs they have 2 numbers on them like 50F8. The 50 refers to the .5mm fuel hole and the F8 Refers to the Air Bleed hole in the side.
A DGV, DFV, DGES mix the air internally in the carb and do not have these air bleed holes in the idle jet. In a DCOE you are acutally tuning the Air and Fuel for the idle circuit with the idle jets. This is a little more tricky but not too bad...Basically you can tune just about any car in the world with an F8 or an F9 idle jet. ( YES there are exceptions to this and I am well aware of them so don't send me nasty e-mails saying that your Mini only runs on F6 idles. This is a basic tuning primer and there is no need to get into vehicle specific problems.) The F8 is Leaner (Has a larger Air hole) than the F9...Soooooo. You can have a 50F8 and a 50F9 and both have the same amount of fuel but the 50F9 has a richer MIXTURE (Less Air to the same volume of fuel.) Generally speaking you should start with an F8 and play with the fuel size until you get close then experiment with an F9 to see if that works any better...

IDF carbs are similar to the DGV and DFV series in that the air is mixed internally. There is no F Number to deal with. The IDA carbs have no Air Bleed Hole but do have an F number to identify this feature. It is an F10. The Air Bleed for the IDA carb is in the Idle Jet holder and it is metered similar to the DCOE. For those of you with multiple IDA or Rotary engines running a single 48 IDA you usually know what you are doing so I won't go into all the details on this.,..
Idle jets are in .5 steps...50,55,60,65 etc. The bigger the Idle jet number the richer the jet. 1 step in idle jet size can make a HUGE differerence. Do not go up or down more than 1 step at a time when tuning the idle circuit.
Choke Tubes and the Main Circuit:
Okay...So now your car should idle correctly, the carbs are synched, the timing is set, everything is good....Time to get the main circuit right. Drive the car. It should come off of idle good and transition to the main circuit smoothly...If it falls on its face and will not take any throttle or runs better if you back off the then you could have a few different problems depending the type of carb. Before you blame the carb make sure you have the Fuel delivery right and the Spark Timing. If you do not have enough advance you will have this problem and it will have nothing to do with the carb tuning.
32/36 DGV, DGEV, DFV and DFEV
These carbs have fixed venturis so the choke size is not an issue. The pump jets are also not a problem. Do not mess with them. If you have a flat spot or hesitation when you first take off then it is likely that the idle circuit is too lean. If you know you have the idle circuit right then the primary main jet is too small. Increase the main jet size 2 steps at a time. (150 main is a 1.5mm hole...Main jets are in steps of 5. eg: 150, 155,160,etc.) Keep checking the plugs after driving it for a few minutes (Do not let it idle when checking the spark plug color for the main jets. Drive the car above 2000-3000 RPM for a few minutes then shut the engine off before letting it idle then check the plugs. If the car then transitions fine but hesitates or falls on it face when the secondary is opened you need to work on the Secondary main jet....
Above 4000 Ft you start having more altitude problems and the vehicle needs to be tuned as outlined here. Another good option is to install a Halmeter AF30 Air Fuel Ratio Gauge to help you with tuning. It is fast and accurate and will take alot of the guesswork out of it. This is a particularly valuable tool for cars that get track use so that you make sure you do not lean out and put a hole in a piston...
38/38 DGES
These carbs have fixed venturis so the choke size is not an issue. The pump jets are also not a problem. Do not mess with them. If you have a flat spot or hesitation when you firts take off then it is likely that the idle circuit is too lean. If you know you have the idle circuit right then the main jet is too small....Increase the main jet size 2 steps at a time. (150 main is a 1.5mm hole...Main jets are in steps of 5. eg: 150, 155,160,etc.) Keep checking the plugs after driving it for a few minutes (Do not let it idle when checking the spark plug color for the main jets. Another good option is to install a Halmeter AF30 Air Fuel Ratio Gauge to help you with tuning. It is fast and accurate and will take alot of the guesswork out of it. This is a particularly valuable tool for cars that get track use so that you make sure you do not lean out and put a hole in a piston...
DCOE, IDF or IDA
Here we go....This is the real tricky part. I feel that Sidedraft DCOE , IDF and IDA carbs are easy to tune but you have to have a real feel for Rich and Lean and understand how the carb works. To get a good understanding of this I cannot recommend too highly to get the Weber Factory Tuning manual and really understand what each component does. That said this is the real Cliff Notes version of tuning the power circuit of these carbs.
Choke Tube or Main Venturi size is the basis for everything in tuning DCOE, IDA and IDF carbs. If you get the Venturis wrong you will never get it running right. Too big and you will always have a flat spot that you cannot tune...Too small and it will always run rich and not make any power. If you have poor throttle response at low RPM
This is a guideline only to get you started or to make sure you are not totally out of range making it very difficult to tune. There are many of you running cars successfully with choke sizes outside this range so don't e-mail me about it. The difficulty in tuning these types of cars is that there are many combinations that work well depending on the engine and the state of tune. That is why everything is tunable. You can tailor the carbs to suit your needs, driving style, engine, location, weather and altitude conditions, etc.....
Here is a very basic chart of what venturi sizes you need to popular vehicles and engine sizes for STREET USE...All out race engines are a totally different story. Use the engine size and HP rating to estimate what you need for your car or engine if it is not listed.
This is a guideline only to get you started or to make sure you are not totally out of range making it very difficult to tune. There are many of you running cars successfully with choke sizes outside this range so don't e-mail me about it. The difficulty in tuning these types of cars is that there are many combinations that work well depending on the engine and the state of tune. That is why everything is tunable. You can tailor the carbs to suit your needs, driving style, engine, location, weather and altitude conditions, etc.....


i have more info on fuel pressures and ignition plus the all important vacumn leak tests you must not have vacumn leaks THAT IS SO IMPORTANT
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Post by Bits & Pieces »

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TURGEM
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Post by TURGEM »

its okk to drill them if you have the special jet drill bits ( i bought from snap on) not cheap its ok to do if you have spare jets i did it to gt my car running right

in the end i found my jet settings are 150 primary and and 200 (or 2mm) for the secondarys which i know is still on the lean side

ill post up the vacumn leak page shortly
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TURGEM
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Post by TURGEM »

its good if you have spare jets lying around its just they so expensive

post them up id love to have a read of that
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Buggzy
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Post by Buggzy »

f@*ken awsome post mate thanks.... and yeah i have re drilled jets myself with success too.
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TURGEM
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Post by TURGEM »

just a little something i forget to mention in regards to drilling jets

if you were to drill these jets to say 150 right (which is 1.50mm) with a normal drill bit the flow characteristics of that jet compared to a genuine weber 150 jet are way out of whack i learnt this first hand years ago and thats why i bought the jet drill bits. they come .05mm increments
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Post by TURGEM »

Ok here is the Vacumn leak Tech Page i promised

I can only hope it helps you guys out


Vacuum Leak Tech Page

All About Vacuum Leaks…Carb and F.I. Systems…..

Okay…This is the biggest problem we encounter with Carb installations and Fuel Injection systems….The big Questions….

What is a Vacuum Leak ?

A vacuum leak is any leak caused when sucking in Air either after the throttle plate of a carburetor or after the Air Metering device on a Fuel Injected car caused by a bad gasket, torn boot, improperly installed adapter plate or manifold gasket, etc….It is called a vacuum leak because the area below a throttle plate or metering device (Mass Air Sensor, Air Flow Meter, Etc.) is under vacuum when the car is at idle and part throttle….When there is a leak in this area you are not “Leaking Vacuum” but rather are sucking in un-metered air…The term Vacuum leak has just been used for so long it is an accepted term

What problems does it cause ?

The major symptom of a vacuum leak is very poor idle quality, stalling, Spitting back through the Intake, and a very lean condition at part throttle….This is the most common problem when doing carb conversions where either adapter plates are used or new intake manifolds are fitted….On a Fuel Injected car with a Mass Air Sensor or Air Flow Meter this is allowing Un-Metered air into the engine..This is a huge problem as the computer is basing the fuel mixture on the amount of incoming air through the flow meter and the extra air sneaking in through the leak can cause a dangerous lean condition..This is especially true of Turbo cars like the Starion-Conquest where the Rubber Boot between the turbo and MAF can be cracked underneath where it is hard to see…

How Do I Find if I have one ?

The best method is to go to the Auto Parts store and get a can of Starting Fluid..This is basically Ether..This is a very volatile substance that is easily sucked into a leak and causes a dramatic change in engine running condition…

With the car at idle spray carefully around the base of the carb or throttle body, at the area where the manifold meets the head, around vacuum hoses and any connections either below the carb base or after the Mass Air or Air Flow Meters…Any noticeable change in idle speed or quality will indicate a vacuum leak

How Do I get rid of it when I find it ?

That is the easy part….Just replace the gasket, hose, boot, or clamp that is causing the offending condition and all will be well again….

Tips for not getting vacuum leaks….

This is easy…When doing a carb or manifold installation just make sure that you have the mounting surfaces VERY CLEAN and make sure you put fresh gaskets on all surfaces. Make sure the hardware is all in good condition and that you tighten the Manifold or Adapter properly..That means that you tighten it evenly and a little bit at a time to insure a proper even crush on the gaskets. If you are using an adapter plate you MUST use Red Loctite to secure the hardware holding the adapter plate to the Inlet manifold and plate to plate in those applications. Also use Blue Loctite to secure the carb mounting nuts…This will insure it does not Vibrate loose causing a leak…DO NOT USE SILICONE SEALER on intake manifold gaskets or adapter plates…The Only sealer we recommend for these Surfaces is Gaskacinch which you can buy from any auto parts store…

Check all Vacuum hose connections and hose to make sure they are secured and not cracked. Any suspicious looking hoses should be replaced. When doing a Weber Conversion very often you have a lot of Vacuum ports that need to be plugged when installing the Non-Smog carb. Make very sure that you plug all unused vacuum ports on the manifold…Even a very small port will cause a leak big enough to make the car not idle…

Basically just be very careful and meticulous about the installation….After you get the vehicle running it is always a good idea to check for leaks before trying to tune the carb.

You CANNOT TUNE a carb or F.I. system that has a Vacuum leak….
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Post by TURGEM »

here is an easier way of tuning your idle


Base line Settings

Speed Screw 1 to 11/2 turns

Mixture Screw 2 turns

Your settings with engine running

Speed Screw______________

Mixture Screw______________




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.

CALIBRATIONS MAY VARY DUE TO REGIONAL FUELS AND STATE OF ENGINE TUNE AND PERFORMANCE. POOR RUNNING QUALITY DOES NOT MEAN A DEFECT IN THE CARBURETOR. AN ADVANTAGE OF THE WEBER CARBURETOR IS ITS EASE OF ADJUSTMENT AND TUNING.

SET UP ADJUSTMENTS

Start set up by confirming carb base line settings. 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. (Checking for linkage bind) Now bring screw back into contact with the lever and continue to open or screwing in 1 turn no more than 11/2 turns.

Set the mixture screw (see Fig 1) by first screwing in until the screw stops, bottoms out. DO NOT FORCE OR BIND AS THIS WILL CAUSE DAMAGE TO THE SCREW AND IT’S SEAT IN THE BODY OF CARBURETOR. Back out the screw 2 full turns.

TUNING

BE SURE TO FOLLOW THE NEXT INSTRUCTIONS IN THE PROPER SEQUENCE, DEVIATION WILL CAUSE THE CARBURETOR TO NOT FUNCTION TO ITS IDEAL SPECIFICATIONS AND MAY NOT PROVIDE THE PERFORMANCE AND FUEL ECONOMY AS DESIGNED.
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. First, turn in the mixture screw until the engine dies or runs worse, then back out the screw (recommend turning ¼ to ½ turn at a time). The engine should pick up speed and begin to smooth out. Back out ½ turn more, or until the screw does nothing or runs worse then turn back to the point where it ran its best.
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. The screw will be sensitive and should only take ¼ to ½ turns to achieve the idle speed you like.
Check and set idle to your driving preference. Put the car in gear and apply slight load, (AC on) if you have AC if not just turn heater fan and high bems on and set the Idle as you like it. Don’t set it too high, as this will cause causes excessive clutch and brake wear. The Idle only needs to be 7 to 900 RPM with light load or AC on.
Recheck timing and vacuum hook ups. Recheck mixture screw to lean best idle again. If all is still best and smoothest idle then confirm and note the final settings.
To confirm settings with the engine running. Start by screwing in the mixture screw and count the number of turns it takes to bottom out and note if the engine dies. If Idle Mixture screws are with in ½ turn of base line setting then all is well and have fun. Also check the speed screw and note how many total turns from initial contact. You may have opened (turned in) the speed screw. Your final setting should be under 2 full turns. Reset the screws (back in) to the best final settings (Per your notes) and go on a test drive and have fun. If the settings are other than described then you may want to recalibrate the Idle circuit (low speed circuit) to your engines needs. This is done by following the rule of thumb BELOW.


Simple Rules for low speed calibration

If the mixture screw is more than 2 1/2 turns out turns then the Idle jet is too lean (too Small). When the mixture screw is less than 11/2 then the Idle jet is too rich (too large). These assumptions are based on the fact that the speed screw setting is not opened more than 11/2 turns. If the speed screw has to be opened 2 or more turns then this is also an indication of a lean condition usually requiring greater change. At times it may appear to be showing signs of richness or flooding it is really a lean condition. See pictures and notes in the tech 2 article supplied in the kit instructions, view and please understand the need to keep throttle plate as near to closed as possible so as not to prematurely expose the transition holes. This is what causes the visible rich condition, and confirms the need to increase the jet size. JET KITS are available if needed.

EXAMPLE With the speed screw set at no more than (1 1/2) turns in after contact with the stop lever; and the best idle occurring with the mixture screw set at 3 turns from bottom, indicates the need for a larger Idle jet. Achieving the best idle at under 2 turns indicates the need for a smaller idle jet.

The secret to understanding the critical nature of the carburetor set up and the advantages of a WEBER over other carburetors is the Idle circuit. Referred to as the low speed circuit by Weber, this circuit is responsible for 80% of the driving operation. This is the reason that the Weber should give a fuel economy improvement over most factory carbs along with significant performance gains. In the worst case you should not see a significant fuel economy loss over stock, while improving HP & Drivability.

The Weber Carburetor is a sequentially timed device to the motor like the distributor. Time taken in the setup will provide more fun later.
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