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B20B Webber carb help

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Old Oct 16th, 2018, 04:36   #1
lelshaddai
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Default B20B Webber carb help

I am running a 1969 B20B in a 544. It has the Webber conversion.
The engine is really running rough at start up. Choke is killing the engine instead on making idle faster. Dwell is at 62. Timing has been tried from 10 to 16 with little difference in performance. Lash is adjusted correctly. Even when it warms up it shakes a bit. I am left with carb issues. It also is bogging down under acceleration. I think it may be a jetting problem. Carb has been rebuilt. It is a 32/36 manual choke.

Right now idle it is jetted, 60 primary, 50 secondary
Air jets are 150/150
Mains are 175/170

I have used idle jets in this combination 55/55, 50/60, 60/55, 55/60
I have used 145/140 on main jets.

Does anyone use this carb and what jets do you use to make it work well?
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Old Oct 16th, 2018, 10:54   #2
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BEFORE you blame running issues on your carb, are you SURE the ignition components are all in good order? Always check, check and check again before faffing around with carbs/injection systems. The 'shaking' at idle you describe sounds like you could be missing a cylinder (as in non-firing). Try new HT leads, plugs, points, condenser, cap and see if that solves the problem.


Got the Weber 32/36 on my B20 - don’t know what size the jets are as it was jetted for a B20 when I bought it as a complete kit from Redline.

Go through the checklist on setting up your carb: http://www.3fowlers.com/Weber%20Trou...ng%20Guide.pdf

Might be worth contacting Weber/Redline and asking their advice about jets. Re-jet kits are cheap and it takes a couple of minutes to change them with the carb on the car, so it’s worth having a go.

Manual chokes can be a pain on these carbs until you get them just right. Take the air cleaner off, get someone to pull the choke out inside your car, watch the activation of the choke mechanism against the throttle assembly: the choke should ‘lift’ the accelerator shaft when engaged (thus allowing the revs to rise at fast idle). You might need to put a sharper bend in the S shaped connecting rod. You can also loosen the screw which holds the choke mech onto the carb, rotate it anti clockwise, re-tighten the screw and try again.

Be aware that you DON’T need full choke on one of these cabs fitted to a B20. I’ve got mine set up so full choke means the 2 choke flaps are on ¾ closed. If you fully close them, your engine will not be happy.

Once you’ve got the hang of setting one of these carbs up you’ll be surprised how good they are.


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Old Oct 16th, 2018, 13:36   #3
Derek UK
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As said, and it's the same with SU's, the first fraction of the choke pull out should just open the main butterflies a fraction to increase the revs. After that, it should progressively close the choke plates. Many Weber users just rely on giving the pedal a couple of dabs to squirt a little gas into the manifold before turning the key and that is often enough when the weather is warm. You have plenty of that. Just using the first fraction mentioned to increase the idle a bit for a couple of miles should stop it going below the normal idling speed until the oil warms up a bit. Again, this is the same with SU's. On a warm day, I can just hit the starter button without touching the pedal or choke and it will start if has run that day. It might have an idle which is lumpy and about 100 rpm down and that's where the first fraction of choke comes in handy.
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Old Oct 16th, 2018, 15:41   #4
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Thanks for all the sound information. I did call Redline. Did not want to give me much information since I did not buy anything from them. I will check the electrical components today and the choke/pump settings.

On another note how easy/difficult is it to replace the valve guides? I replaced the stem seals but still get smoke at shifting under load(going up or down hill)
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Old Oct 16th, 2018, 22:52   #5
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Your jets are pig rich!

However, the first ting you should have done before installing the Weber is to flip the carb upside down and count how far in you can screw the idle adjustment before you expose the progression holes. If you have exceded this, the carb will be impossible to tune correctly.
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Last edited by saintlyvolvo; Oct 16th, 2018 at 22:58. Reason: Fault
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Old Oct 16th, 2018, 22:56   #6
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This car came with the carb already installed. I have just been trying to get it to run better. What jets do you suggest for it? And I’m not sure I understand what you mean by the progressive holes? I can take the carb off and look at it again. But I just need to know and understand what you want me to do.
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Old Oct 16th, 2018, 23:10   #7
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Take a look at this: https://www.jeepforum.com/forum/f8/w...ssion-1051137/

There are no standard jetting, but common combinations do excist with the B20, like 55/50 idle jets and 150/145 mains.
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Old Oct 17th, 2018, 12:42   #8
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Default Weber issues

I cant comment on this particilar weber but the principals are the same for all.
I have a set of Solex ADDHE which are similar to the DCOE which again is similar in principal to your carb.
Everything appears to point to fueling
Assuming the ignition is spot on (use the basic B20 specs is a good startng point). You wont tune any carb if the ignition specs are not correct
Spark plugs - what colour
Idle screw. 1.5 turns out - if more than 2 then idle jet is too lean if less than 1 then too rich. Change out in tranches of ten
Idle jet - typically should correlate to the choke size i dont have the calc to hand
Main jet - again correlates to the choke size change in tranches of 5
Air Corrector- minimal effect below 3500 as most of the air is coming via the emulsion and idles (idle jet is a mixture of fuel and air)
Finally emulsifier - these are rarely changed and if the car has been running right on this engine i would suggest to leave well alone. If it has never run right then you need to check that. I may have some baseline specs somewhere
One point re the progression holes.
If they are uncovered with the throttle plates on the stops then you are masking the problem. In effect you are adding fuel when it shouldnt be added. The ‘system’ should be soley on idles up to 1500. If the progressions are uncovered below that then its supplementing the idles. The progressions only fill the ‘hole’ between idles and mains.
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Last edited by tdz840; Oct 17th, 2018 at 12:45. Reason: Cant spell or type
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