Carburetor Central
If you have questions about the SU Carburetors, this is where you can find the answers.
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Since first firing my rebuilt 2.4 engine back is September, I''ve probably run it for about 20 minutes. But now it won't start, and the problem seems to be that the new, Kyosadenki mechanical pump has stopped pumping. There is fuel to the filter side, but none comes out the carb side. Anyone know of any reason why a new pump would fail? I took if off the car and bench tested by pushing the lever while hold a thumb against the inlet. Sounds OK. Also, when I removed the pump, it appeared that some fuel may have back-flowed into the engine - likely oil change time. Any thoughts or suggestions would be appreciated. With respect to the carbs, both the SU bo…
Last reply by jalexquijano, -
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I have read that the twin Hitachi SU carbs in our cars can only handle 4 PSI from the electric fuel pumps. My mechanic recommends swapping my electric fuel pump with a Facet Silver Top and regulator: https://www.pegasusautoracing.com/productdetails.asp?RecID=85 I am really aiming at a noiseless or very silent fuel pump that will keep on pumping gas even when decelerating at corners.Is the above fuel pump recommended for a 240z?
Last reply by jalexquijano, -
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I rebuilt my pair of carb's using Z-therapy's kit. My rear carb seems to function correctly but the piston sticks and does not fall to the bottom in the front carb. I tried moving the orifice around to better center the needle but then out of desperation, removed the needle and it still is getting stuck so it's not the orifice or the needle causing the binding. I also tried switching the dashpot domes front and back and the front one still sticks. The piston moves freely only with the dome off. I've read where people say never to remove metal (e.g. sand) the dashpot dome and elsewhere where it is offered as a suggestion. Does anyone have an idea how I should re…
Last reply by siteunseen, -
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Hello...Newbie to Z-cars, Old hat with British Cars. I resurrected a 73 240z from my buddy's garage. His wife bought it new. When I first got it I drained the tank and put in a few gallons. No gas would flow so I blew out the fuel line from under the filter under the hood. I heard it "bubbling in the tank and it fired right up...! Every so often, I would have to do that line blowout and I could drive the car for 30 or so miles. Now even that won't get the gas to flow. I disconnected the fuel line from the metal line at the rear and gas is flowing. I blew out the line between the fuel filter and the back without it being attached to the tank. I blew into the tank without t…
Last reply by siteunseen, -
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Here is all you need to know to set the fuel level in a fuel bowl for 240z from 1970 to 1971 inclusive (You will have to deal with the oddball bowl in the 72's however the FSM states that the fuel level will be the same in each bowl). Below are two marks at 20mm & 23mm down from the top lip of the fuel bowl. The FSM shows the fuel to be 23mm down from the roof of the fuel bowl(which is 20mm down from the top lip but it may be a typo. Pick one and be happy. The great Brian Little transposed the 23mm down from the top lip of the fuel bowl to a depth from the top of the bridge in the carb throat. He came up with 10mm down. I repeated…
Last reply by siteunseen, -
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Both of my 3 screws su carbs were rebuilt by ztherapy in November 2014 as per the sheet attached. However, i have noticed that if i dial both fuel mixture knobs to 3 turns clockwise, the front carb spark plugs still turn out leaner than the rear carb spark plugs. Could there be a mistake on the sm needles diameter provided by ztherapy? Could they have mistakenly installed different needles on one carb and on the other and the adjustment is not paired.
Last reply by esmit208, -
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Hi everyone: I spent three days using the 10 turn down method to set my float levels. It’s maddening but I was so happy when I finally did it. I'm trying to set idle and sync the carbs. Both jets are set at 2.5 turns. I am able to get the engine to stumble along when I disable the rear carb. However when I disable the front carburetor the engine quits immediately. I lowered the rear jet by a 1/4 to 2.75 turns and still quits. Lowered rear jet to 3 turns and still quits. So I took off the rear dome and turned down the jet ten turns to check the float level. The fuel level is just a hair below the opening. I called it the day at that point and now I’m hopin…
Last reply by 882993md, -
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I have a 73 w/ L28 & tripple webers & have always had a lil problem with the fuel supply being unstable. The pump just went out, so I replaced it with a carter 4070. Come to find out the pump that was on there (I thought it was original) is a mitsubishi pump. Did mistubishi even have a performance carb'd car in the us? Anyway I put the carter on yesterday & the car had more power & didn't bog or stumble at all. This morning on the way to work it kept flooding to the point it would stall. I have a switch for the pump & had to turn the pump off for a min as soon as it started to bog (all the way to work). I'm sure it needs to be tuned now but, the second…
Last reply by jalexquijano, -
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OK, I used my Float Sync tool and a color tune spark plug to set up my SU's today. All went relatively well, but having the advantage of seeing what is going on in the float bowl with the Float Sync caused me to have a question. When off of idle, (hand race engine), the front float bowl level is dropping, the rear is stable. Under load I believe the car will lack fuel in the font carburetor. My first thought is that the fuel pump is not pumping enough volume for both carbs. I am sure someone has a better grasp on this and understands why the back carb would get the fuel it needs as apposed to the front. See Video. IMG_0746.MOV
Last reply by Stanley, -
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Hi all, I'm still dealing with a high rpm issue, but I'll leave that to another thread. What I would like to know is the float level for 1972 carbs; I hear that they are not the same front and rear. I believe the typical level ('70 and '71) is 23 mm measured from the bottom of the lid to the fuel level with the floats in the fuel bowl. Measuring from bottom of lid to fuel level (using clear plastic hose from fuel drain and aligning it up against side of bowl.) I can get a level of 1 inch (25.4 mm) pretty easily for both carbs. Is this close enough? I'm getting pretty good with the whole procedure, but it's still fairly time consuming. Unfortunately, so far, all my…
Last reply by David F, -
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Hi everyone, I took off my needle valve on the front carb to clean and I stupidly dropped the brown washer into the engine bay. I have searched under the car and inside the engine bay (in the nooks and crannies) for one hour and I can’t find it. ☹️ Does anyone know if this is a ztherapy only part, or would a Napa or Pep Boys stock the washer? I was hoping to have my car on the road tomorrow and now this happens. Howard ‘74 260z
Last reply by Patcon, -
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I have several questions regarding the precise fuel pressure both of the 3 screws round SU CARBS on my 240z will tolerate as i am pushing the fuel through an AIRTEX 8012S which is rated 5 to 9 PSI: 1. Should i measure the fuel pressure plugging a "T" before the front carburetor? 2. Should the pressure read no more tan 4.3 psi? 3. What if the pressure reads more than this limit but does not show any spill out of the fuel bowls? Will i need to open both fuel bowls and reset the level. THis was done by Ztherapy in 2014 and i would not like to mess with it.
Last reply by Patcon,
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