Carburetor Central
If you have questions about the SU Carburetors, this is where you can find the answers.
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So I have never been particularly happy with my Cannon manifold for the triple Webers that I run. As many of you know, the alignment of the rod ends that are tapped into the manifold and not particularly accurate and as a result it has been necessary to remove the middle rod end so as to minimize binding of the throttle rod. I have always had issues with this setup in terms of "return to idle" and this misalignment exacerbated the whole setup. I have also had to use external return springs which just add more clutter to the engine bay as well. So the primary motivation I had for this upgrade was to achieve a smooth return to idle regardless of whether I was successful…
Last reply by Rio24, -
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I am in the process of tuning the round-top SUs on my 71. The first step is to set the idle screw and and jet level. The jet is supposed to be even with the "bridge," the flat part where the piston comes to rest when it is "at rest." This is possible on one of the carbs, but I cannot raise the second jet high enough. It is about a 16th-of-an-inch below being the bridge, I cannot get it to a flush position. Is it possible to loosen the jet jet locking nut and then make a "gross" adjustment so that I will be able to set the jet to flush using the jet adjusting nut? An other way of putting is, if I was rebuilding my carb how would I know where to place the jet befo…
Last reply by DannDZ, -
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... is a batch of fuel rails just back from plating. Its Fuel Rails Fiesta time, coming soon to an advert near you!
Last reply by SoCalJim, -
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I am attempting to tune my '71 with the old round top SUs. I performed a rudimentary (at best) carb tuning and then turned to the ignition. While tuning the engine I was able to get the it to idle well at 800 RPM and it had strong acceleration up to about 6K RPM and 90 MPH. (On a track only, of course! ?) But when I look at the ignition timing with a timing light, it shows that it is about 25-degrees BTDC! The distributor is at its limit of adjustment. Is it possible/recommended that I remove the distributor itself and move it by "one position" to fix the problem and get me back to the right range where I can make timing adjustments just loosening the distributor cap…
Last reply by Zed Head, -
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I have a question for the carb guys, when I adjust / sink my carbs it idles smooth. then on another day when it is humid out and the temps change it idles rough. I can not seem to find the sweet spot with weather, I think it is weather related ? off line no stumble, mid range and top end pulls great it is just at idle? my idle rpm is 730 rpms in gear and it does not matter in gear or out or gear it does not idle smooth. plugs are perfect color , my timing is 15btdc with vacuum plugged. any thoughts would help just like to have a smoother idle. thanks
Last reply by kully 560, -
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Hi, first of all i want to thank everybody on this forum for always pointing me in the right direction with my Z so far. I am still in the process of learning and understanding the car and trying to identify and fix as many issues as possible. The car is a 280Z with a F54 L28 in it with P79 head and Ztherapy SU carbs (4 screw). Exhaust header is a Zstory Street into Zstory 2.5" full system. The carbs were tuned with the help of a colortune until it showed a bunsen blue (first 1 then 4). This resulted in the fuel mixture nut to be turned a little over 2.5 revolutions down (measured both sides with calipers: 2.7mm down). As mentioned in an earlier post the idle i…
Last reply by Johnny280, -
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A fellow on FB (Mark Shep) just posted a quick article about how he replace his choke cable sheath and core wire. He showed poictures of what he had done and he gave us the URL of the company he found that supplied the wire and sheath. Just had a quick look, seems that have quite a bit of inventory. Should be useful to use in the future. http://www.controlcables.com/ He measured the stock sheath and told them what he needed and they set him up, so we don't have specific part numbers but now we have another vendor to somehow remember.
Last reply by hls30.com, -
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new 71 240z owner. just balanced pair of SU dome carbs with Unisyn, using instructions from ZTherapy. car now runs OK, but thinking it could be better. for my 70's Ducati twins, use my Twinmax electronic carb balancer. two hoses go to two fittings, one on each intake manifold. no moving a single air flow meter back and forth, can easily see relative vacuum suction, easy to tweak idle speed for pulling same vacuum at idle/5000rpm, tweaking so each carb starts increasing vacuum at same time, when throttle is opened. wondering if anyone else has tried this or mercury sticks. could do an experiment by drilling/tapping carb insulator blocks (could also use the intak…
Last reply by Captain Obvious, -
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The puzzlements never end. With new ZTherapy needle valves in place, and having set the float-bowl levels at 23 mm on a bench-test, glass jar I rigged up, I found my carbs suddenly worked far better than when I used the plastic-tube-attached-to- the- bottom-of-the-bowl system. Car ran nicely. But for whatever reason, the front carb is now blowing fuel out its vent tube. Remove the float lid, and everything looks fine; the float pivots as it should, and the new needle valve moves smoothly. But I`m still puking gasoline. Any thoughts would be appreciated.
Last reply by siteunseen, -
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Found this video on a cheap vapor lock solution. While I never had a problem, I know several others here have. Thought I'd give you the heads up.
Last reply by djwarner, -
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I am one of the many Z owners, with SUs, that has battled a lean condition on hard acceleration, or WOT. My idle and cruise AFR readings (have AFM attached to header) are great at 14.5 or so, so have adjusted it as best as i could. Along with SM needles, I adjusted fuel levels and tried to do anything I could think of to resolve this issue, to no avail. I even switched to triple Webers, which allowed me to see how my car could really perform with appropriate AFR! I decided to switch back to SUs, as I had some linkage sticking and fuel dripping that bugged me. So, I started looking into the different available SU needles to see if I could find something richer. …
Last reply by moritz55, -
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Hello, I am fairly new to SU carbs and have a few quick questions. I have a 1973 Datsun 240z with 3 hole SU carbs. I was driving the car the other day and noticed that I was loosing power at WOT. I got the car home and it was idling low and died out on me in the driveway. I popped the hood open and noticed that the rear carb was leaking from the lower nozzle head or hose onto my header (I don't want to burn my car down). I also noticed that the float bowl was loose (loose meaning I can take my hand and rock it back and forth)and some fuel was coming out of the top float nipple. Sound like I have a couple of issues here with the float and/or lower jet nozzle/noz…
Last reply by Dan222000,
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