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blawrence Member
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Cannot seem to get fuel/air mix lean enough. Maybe a new needle is needed in the strombergs. Does anyone know where to get replacement needles? Is it always the needle that wears or does the orifice wear too? |
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Arvin Appelman Member
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I have never had to replace the needles unless they are pitted these items don't typically wear. Are the float levels set and needle valve closing? Other things to check would be the fuel pressure, chokes fully open, and air cleaners. |
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Frank Schwartz Member
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Arvin: I think Delta sells the needles and you would probably want to get the seat as well...I also think Bruce Madden has them...in fact, I think I bought some from him years ago. Frank |
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redracer Member
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Yes, both the needles and to a lesser extent the orifice wear due to the design. Unlike SU carbs where the needle does not touch the sides of the orifice, the spring loaded Strombergs were designed to have the edge running against one side of the orifice, making the faster wearing needle run rich, mostly at idle. Use a CO meter to adjust the mixture to 4% at about 3000 rpm and don't worry about the idle mix (unless your state still requires mandatory emission tests). |
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xman Member
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I recently installed a rebuilt pair of strombergs on my car. I took extreme care to get the float level correct and to avoid any vacuum leaks. The metering needles were brand new. The mixture was too lean;no matter what I did. The throttle shafts were new too. I had to install the old needles to get the proper mix. On visual inspection the old and new needles appear different. The new needles are longer and seem a little thicker at the base. That would make it lean at idle. Has anyone else had a similar experience? The worn needle would give richer mix. I had the new needles adjusted fully clock-wise and still too lean. I got the new needles from two of our common sources. |
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noomg Member
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xman, It sounds like you got the wrong needles or your jets were not set to the proper level (too high). There are literally dozens of metering needles available for Strombergs depending on the application. I don't know what your common sources are but I know Delta sells the correct needle. |
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xman Member
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Thanks for weighing in. I think I have the wrong needles too. I bought them a few years ago and used them on carb rebuilds during quarantine. I just installed them last week. One pair came from Delta and one pair from Joe Curto. All four are stamped B1DK. I think they are defective and/or mislabeled. Those things require very precise machining. I doubt they come from the UK anymore. Glad I hung onto the old ones. Car runs great now. |
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redracer Member
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If you got your needles from Joe Curto, they should be correct: B1CM for early engines, and B1DK for the later ones. I had Joe make me some about 30 years ago, and they are the correct length and size(measured to 10 thousands at 13 places). |
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Darth V8R Member 
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What makes you say the needles are too lean? Are you using the "lift the slide" technique to read the mixture? It is extremely technique sensitive, and if done incorrectly (as it almost always is) it will show the carbs as lean. When using the lift the slide technique, you lift the slide approx 0.5mm (0.020"). The engine speed will change according to the mixture but only for about 2 seconds, and then will return to a normal idle. If the normal idle does not return, you did the test incorrectly (probably lifted the slide too much) so try again. The idle speed will change a very small amount (less than 100 rpm) so you must listen carefully. If this sounds tricky, it is because it is. I gave up trying to get repeatable results, and now use plug cuts exclusively. You can also use a color tune or O2 sensor. As to a source of needles, the best source is Burlen Fuel in the UK. I counted about 80 different needles for the Zenith carbs using the 0.10" jet, and a similar number for the smaller Zeniths. Be aware however that Burlen's web site lists only a small sample of what they carry. Get their hard copy needle catalog and it lists everything. If you know which needle you want, you can do a search on their web site and the needle will come up even if it is not listed in their on line catalog. Joe Curto is also an excellent source, although he does not carry every needle. Vance Last edited on 03-10-2023 03:43 am by Darth V8R |
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xman Member
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Thanks for the tutorial on the "lift the slide method". Everyone seems to have a different take on that. It sounds like you have a lot of experience with it. With the new needles if I raised the air valve at all the idle fell off immediately. Besides listening, I also have an analog tachometer hooked up. The old needles I had seemed to adjust properly to a point where lifting the piston caused no increase in idle speed. That's good, right? I also looked at my spark plugs. It would be great to have an exhaust gas analyzer or better to know someone that did. I will definitely check out Burlen Fuel. In the meantime the car is running great on the old needles with the rebuilt carbs. When I get some miles on it, I will take another look at the plugs. |
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Esprit2 Member
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After trying the usual suspects (JH & Lotus parts vendors), I believe the best Zenith-Stromberg resource in the USA is Joe Curto, aka British Superior, https://www.britishsuperior.com/services |
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