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Thread: Weber jetting correct?

  1. #1

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    Weber jetting correct?

    Okay so i finally got around to seeing what jets this thing has in it. Not sure if im gonna get the names correct but here it goes.
    At the bottom of the bowl the primary fuel jet is 140, the secondary fuel jet is 155. On top of the carb/bowl (air jets??) The primary air jet is 170 and the secondary air jet is 160. Do those sizes sound good for a 2.0?

    Background, truck runs rich around 16mpgs. Choke has been set, idle mixture adjusted, idle adjusted, float has been adjusted.

  2. #2


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    Lets start with, there is NO correct or incorrect jet settings. There is ONLY what works and what does not For You!
    Based on but not limited to these conditions.

    A. What model Weber you have.
    B. Your Motor+Mods if any: Stock, Slightly Modified, Slightly Highly Modified
    C. Your Location: Altitude, Temp. etc..

    The only jets you did not list is the 2 most important Primary and Secondary Idle jets these, control your fuel from idle to about 3k rpm's where most of your driving occurs.

    Do you have a tuning guide. Remember it is just a guide NOT gospel, use it as a staring point and either increase or decrease jet size for YOUR needs and it is always better to run a little rich than lean and burn a valve.

    TIP 1. it is not a HOLLEY, CARTER etc..So it does not tune the same

    TIP 2. If it stumbles, hesitates, falls flat, coughs it is usually A LACK OF FUEL

    TIP 3. If while running and snap the throttle open a slight pause is all that should happen with a little puff out the exhaust.

    TIP 4. Repeat Steps until Tip 3 is achieved.

  3. #3

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    Damn there's idle jets too? I'm gonna be an expert with this damn carb by time i get it running how i want. Alright thanks for the info, i'll have to check and see what size the idle jets are on it.

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    What Weber do you have 32/36 Progressive 38/38 Synchronized.

  5. #5

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    Its a 32/36 DGAV.

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    Primary Idle jet is depending how your carb is oriented behind the choke Big flat head secondary opposite side. (3a)


  7. #7

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    Here are the the jetting sizes for a 32/36 DGAV relating to a 2000cc engine-

    Main jet - (primary throat) 1.35
    (secondary throat) 1.30

    Air Correction - (primary throat) 1.75
    (secondary throat) 1.45

    Emulsion tube - (primary throat) F50
    (secondary throat) F66

    Idle jet (primary throat) 0.50
    (secondary throat) 0.50

    Idle air (primary throat) 1.50
    (secondary throat) 0.70

    *bearing in mind that the venturis are the right diameter for your engine, this is only a base line guide.
    I've used 'primary' instead of the term 'progressive' - I think it's easier to understand. And the jetting seems to be too big for your engine, especially the main jets (the above chart shows the primary main being the bigger jet)

  8. #8



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    progressive is how / type the secondary opens.
    Members come and members go, But the board keeps track of them.
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  9. #9

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    I have a suspicion that the figures on the jetting recommendations for the mains were recorded in the wrong order (I would find it weird that the primary would run a bigger main jet than the secondary). Looks like your 32/36 might have been jetted for a 2.6. Even so the 160 secondary main jet is BIG - should be 1.45/1.50 at the most for a G63B. Same goes for the air correction jet - go down to the correct size (the massive secondary main + air correction jet = dumping fuel). Change the secondary main jet and air jet and you should get mpg improvement and general top end power. Maybe upsize the primary air correction jet to 1.75 and you should get a bit more power down low. Have fun Mischif and let us know how this goes for you.

  10. #10


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    Also Don't forget all changes and adjustments should be made while trying to simulate driving conditions ie with air cleaner on it really does make a difference.

  11. #11

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    I ran into this last night in search of the formula to determine what is the best size venturi to suit a shared plenum intake (I came up bust but I did find out a lot of other useful info). This might have a link posted somewhere else but I'll chuck it in here - http://www.fordfe.info/CarbMythFact.html
    The observations made in regards to carburettion aren't specific to an engine type or carb (he uses 2BBL vs 4BBL for comparisons of CFM) but if you're an engine NERD and are interested in the formulas to calculate ball park fuel delivery tuning then this will be very helpful.

    He then goes onto header design and how that has a direct correlation to HP (air in - air out) and I know there are guys here who are onto R&D of their own headers so I also checked this out - http://www.superstreetonline.com/how...m-made-header/
    (this went straight over my head - me and algebra are not good buddies) If I had the skills and time I would be all over this!

  12. #12



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    Weber does have basic rules also for weber carb adjusting. So many turns out, So many turns in and if it doesn't fall within this specification then you make jetting adjustments accordingly. In our manuals section of this forum, there is a weber manual dealing specifically with the weber. This may help you also. Depending on your elevation also can determine requirements in jetting.
    I would do a basic check on how many turns that mixture screw is out and start there. The 170 seems a little off to me since I think I use about a 165 with headers, short dump exhaust, ported head and a race cam @ 2000 foot elevation, which elevation doesn't make a huge change, but it has some effects.

  13. #13

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    I still haven't gotten around to checking what size the idle jets are. I kinda pushed it aside since i got the truck running at about 26mpgs now. Interesting that you guys say it has bigger jets than what it needs. That would explain a few things. Doing anything over 70mph on the freeway and my mileage drops alot. Fast acceleration in the lower gears and it drops as well. Also it feels like the truck has no real power passed like 50% throttle and my best guess would be around 3krpm(no tach). Oil also still shows signs of fuel contamination. I'll have to give weber a call sometime next week and order some more appropriately sized jets.

  14. #14


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    3k is right around where secondary circuit takes over and runs to red line.

  15. #15

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    Quote Originally Posted by Mischif View Post
    ... it feels like the truck has no real power passed like 50% throttle and my best guess would be around 3krpm(no tach). Oil also still shows signs of fuel contamination. I'll have to give weber a call sometime next week and order some more appropriately sized jets.
    Your engine is drowning in fuel (this carb may have been tuned for something like a 3.9 - 4 liter 6 cylinder) Jetting the secondary down will radically change how your truck performs and save your coin for other things (like that trick cam and tasty headers you're going to get in the future )

  16. #16


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    Just noticed, it wasn't asked or said what fuel pump / what are you running.

  17. #17

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    ^good spotting mopar ja. No fuel pressure reg or not running a low psi pump will wreak havoc with the Weber.

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    I run an AC EP42S electric fuel pump for many years. It was recommended by Top End Performance when I bought the carb. Been very happy with it. It is mounted by the fuel tank,below the tank on a little bracket that was already there.

  19. #19


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    This makes a world of difference Webers like fairly low pressure with higher flow/volume that is why i went with the Carter 4070 rotary pump.

    And a side for a bit of fun and controversy Pumpernickel "IS THE BEST RYE BREAD EVER. PERIOD!"

  20. #20

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    Still haven't gotten around to checking idle jets or calling weber. Had some bad luck with the truck. Got in a dispute with a machine shop over some charges, walked away to go pull money out, and when i came back my key no longer wanted to go into the ignition switch. So after getting our shop tow truck to come pick me up i pulled the cylinder off. Looked like someone jammed paper in it. Then on the drive home my alternator finally gave out. Thing got towed twice in one day haha.

    Anyway, my fuel setup is this. Some cheap 15 dollar electric pump off ebay. I think it was rated at around 4psi and 30 gph. When i tested it, it put out 8 psi. So i picked up a regulator and have that set at 3 psi.

    This next week im really going to try and find the time to check those idle jets and also give weber a call about some jets.

  21. #21



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    see how it runs now with the proper pressure and the mileage works out to. The jetting may be alright - too high a pressure will force the fuel past the needle and seat and flood out the motor.
    Pennyman1
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  22. #22

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    Quote Originally Posted by Mischif View Post
    ...had some bad luck with the truck. Got in a dispute with a machine shop over some charges, walked away to go pull money out, and when i came back my key no longer wanted to go into the ignition switch. So after getting our shop tow truck to come pick me up i pulled the cylinder off. Looked like someone jammed paper in it. Then on the drive home my alternator finally gave out. Thing got towed twice in one day haha.
    What a bunch of a-holes. If you send something into a shop to get it worked on and they run into an issue (whether its a part price issue or an unforseen problem that requires more effort and time), they should be ringing you first and asking where do you want to go from there. It is common courtesy. Then they sabotage your truck - in a really childish and pathetic act. The alternator dying is just another one of those things that fail without much warning but look on the bright side - you can get a replacement one with higher output now!

  23. #23


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    Sounds like time for BBB report and or Post on Rip off report and word mouth about their service. Might also want to check the flow on your fuel regulator, most of them work by restricting flow.

  24. #24

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    Finally pulled the idle jets. Primary is a 60, Secondary is a 50. How do those sound? So i was thinking instead of getting the right size jets how about i just add more air with a little snail . Lol jk, well maybe...no i can't..hmm.

  25. #25


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    Those sound about right, also you adjust each side independently from each other.

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