SU Carb Technical Articles
Various articles and how-to's.
59 topics in this forum
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Hi all, Does anyone have good step-by-step instructions for adjusting the Choke Cables on SUs? I'm having a hard time finding an adjustment wherein a) the Nozzle comes down with Choke on, and b) the idle is reasonable (~ 900) with choke off and engine warm. Thanks!!
Last reply by jalexquijano, -
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- 42 replies
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There is a fine screen filter in the banjo fitting, but it is after the main and finer filter, so just wondering if it is needed? Has anyone found new bushings for the main butterfly valve shaft or a way to stop the air sneaking through the gap? Is there a trick to getting the needles out without damaging them? I've unscrewed the slot head screw holding them in place but can't get the to budge.
Last reply by Captain Obvious, -
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- 7 replies
- 907 views
Anyone in or around upstate SC know of a good mechanic that can tune my new z therapy carbs on my 240Z?
Last reply by AK260, -
- 2 followers
- 5 replies
- 790 views
Ok, I'm having a bad week with nice stock L24 with SU's. Runs fantastic until you get over 4-4.5K RPM, then it leans out and misfires. Facts and Observations SM needles (been trying several others....) Four screw early carbs. Fresh and minty. New AEM AFR gauge in the exhaust. Never leave home without it. AFR's 13-14 around town below 4K RPM, car pulls like crazy super smooth 800 RPM smooth idle, but crawls up to 15-16.5 or higher and misfires when you get over 4K. Doesn't fall on its face, just gets rough running and power falls off and has trouble getting to 6k RPM. Fuel deliverability confirmed. NOS stock pump and then with an NOS electr…
Last reply by Captain Obvious, -
- 6 followers
- 15 replies
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Apologies if this has already been discussed, but as I work to bring my '71 Series 2 back to original, I remain puzzled by the coolant line running through the intake manifold. I've now reconnected it, but only for appearance purposes. When a car is first started, the coolant is, as name suggests, cool. So how can it have any effect on smoother running when still cold? But on the other side of the equation, once the engine warms up why would we want to be heating the intake manifold? Having the coolest intake charge is fundamental to performance is it not? The cool fuel mixture is more compact and will there expand to a greater measure at the point of ignition. …
Last reply by siteunseen, -
- 2 followers
- 6 replies
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Combing through my laundry list of odds and ends, noticed my carb linkage has a floating plate looks like a mod for sure, was just wondering if this is a problem ? I have a lot to learn and I appreciate any and all input !
Last reply by Dat.240, -
- 5 followers
- 11 replies
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When stopping at a red light the idle lowers on my round top SU carb 260z.It takes anywhere from 3 to 15 seconds to increase by itself back up to 800/ 900 RPM. It lowers to about 500 RPM and as mentioned increases slowly back to regular idle speed. If I pull away from the light before the idle increases the car stammers. What is causing this, vacuum leak, vacuum advance issue or something else. How can I fix this. Some additional information the connectors on my carbon canister are broken so they are not connected very well- would this cause it....Thoughts , suggestions???
Last reply by zdude1967, -
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Does anyone know of a source for a replacement OEM or OEM equivalent for the heat riser tube from the exhaust manifold to the air cleaner? Thanks in advance for your help. JLP
Last reply by AZ-240z, -
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Recently picked up a used set of 3-screw roundtop SU's that I plan to restore as a back-up set and last night when I was disassembling them, I noticed the needles are engraved as "369". The previous owner said that the carbs were from a '72 SCCA racer, so I'm guessing they're richer needles. I was really hoping to see a ZT serial number on the throttle shaft, but I couldn't find one, but the floats do appear to be newer and the rest of the carb body appears to be in good shape (under about 20 years of dust & grime). Has anyone heard of a 369 needle?
Last reply by siteunseen, -
- 1 follower
- 1 reply
- 2k views
Hi all, Can anyone identify the signature on these SU Carburetors? They're on a pair I just purchased on ebay, and am preparing to for installation. The first name appears to be "Landa". The last name starts with an "A". Ringing any bells? (Just curious...) Thanks, JH
Last reply by siteunseen, -
- 2 followers
- 5 replies
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Greetings! I’m in the sharing mood again, so thought I’d share an episode from the series “I have no idea what just happened, but you won’t believe what the solution was”. Yesterday, local Z owner wants to drop by for an SU tune on a recently acquired late 71. It’s “running” but is overheating and doesn’t run “Well” overall. Suspect mixture too lean or fuel supply lacking. So do the usual, no need to bore you with details, but here is the overview, no order intended. Bowl fuel level Fuel pressure air flow sync linkage evaluation. How many turns down for the knozzles, Nozzles were down 1 turn on the front and 1.5 turns …
Last reply by SteveJ, -
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Some things just become matra’s. With SU’s, people ask you how to know if the ones they have or are about to buy, are worth anything, and the “Standard Response” is “wiggle the shafts and see if there’s play” as they cause a vacuum leak. Then we typically add to that “get Z-Therapy to rebuild with their cool sealed shaft bearings”. End of discussion Well as I’ve come to discover there is another nasty vacuum leak area of concern on SU’s that I think is JUST as prevalent as shaft wear. The nozzle fit in its sleeve is often very worn.
Last reply by zKars,
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