Carburetor Central
If you have questions about the SU Carburetors, this is where you can find the answers.
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Yup.... got 30mpg (Imperial Gallons) cruising at ~ 3,000 to 3,500 rpm on a 240z. Idle jets significantly impact cruise fuel efficiency. I was experimenting and used two sets of idle jets: 1) 55F11 2) 55F9 with air drilled from original 1.0mm to 1.5mm (picked up some metric bits in Lisbon) I installed bolts in place of the spill jets to rule out accelerator pump leaks clouding the results...btw it is not so bad driving w/o acc. circuit. The 30mpg was attained with 18.5 a/f at idle and 14.7 to 15.5 at 3,000 rpm over flat road. The idle was rough and difficult to maintain at ~ 800rpm and 2 turns out on the mixture screws. I drove ~ 300km and eventually developed som…
Last reply by siteunseen, -
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- 18 replies
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presently 40DCOE151 125 main 170 corrector F11 emulsion 30mm Choke 4,000 RPM 11.5 Air/Fuel 6,000 RPM 10.5 Air/Fuel 240z L24 270 cam I am thinking that a switch to 115 may lean it towards 12.5 at 4k and at the same time tip the the high end back at 6k. Any suggestions?
Last reply by Lazeum, -
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I am starting to look deeper into the claim that later DCOE's Idle Enrichment Screws are typically turned-out further. The details in the screw interface to the carb body distill to: 1. For the same flow: A narrow tapered needle needs to be tuned out further than a wider tapered needle if the orifice size is the same. It is proportionate to 1/tan 2. For the same fuel flow, a needle with the same taper needs to be turned out more from a smaller orifice than for a larger orifice. So to compare an early carb's Idle Enrichment Screw turn-out to a later, one must know the taper of the needle and the orifice size. In another post I measured the threads on early and…
Last reply by Zedyone_kenobi, -
- 6 replies
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I just tried the choke on triple DCOE 40 151's with the default choke jets/tubes/air that came with the car. It seems to be too rich and no fast idle. Can someone describe how 3weber chokes are supposed to behave when properly set up? What will the idle jump up to when engaged? What A/F should I aim for? Thanks
Last reply by Lazeum, -
- 4 replies
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Hooked up my new FP gauge today, like the gauge it's a 0-10 psi McDaniels, easy to see under glove box from driver seat. Line is steel braid over Buna-N with black braided Dacron cover good for 3025 psi, all OK. Got steady 3.8 psi at idle which is ok I guess. Bled out the air, think I got most of it. One question though, when I shut down the engine, FP drops fast to 3 psi, then very slowly to 1.5 or 2. After a minute or two, looked at it again - it went back up to about 4 psi again. Whaaat? Then it dropped off again. After 15 minutes it was down to 1 psi. Doesn't seem like much of a problem, but I don't get that strange behavior at all. Any ideas? I got zip.
Last reply by Stanley, -
- 11 replies
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I bought these from a acquaintance type who said the car was running fine with these carbs. They have been sitting for two years. I am getting ready to install them and came across the linkage issue. My question is how come two of three carbs don't have the throttle linkage no where near the idle speed screw? The throttle plates of those two are open as far as the linkage is from the screw. I can't find the adjustment procedure in all the literature I downloaded from this site. All I have figured out is the throttle shaft hits the accelerator pump rod. I appreciate the help!
Last reply by 240260280z, -
- 6 replies
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Hi, I've reached the carb set up stage of my restoration now. I've got a colour tune and a uni-syn so I started with trying to balance air flow. I set the uni-syn so the front carb bought the little float up to around the centre mark of the tube and then tried the rear carb and it's not even registering on the uni-syn at all. I would screw in the throttle screw but at the moment the rpm is really high even though I've got both individual throttle screws backed out all the way, and the screw on the main throttle linkage is also backed off all the way. I read somewhere to check for vacuum leaks with carb cleaner so I will try that tomorrow but I was wondering if someone co…
Last reply by z74z90, -
- 0 replies
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Walmart had one so I bought them both, G3 & G2. G3 is 3/8's G2 is 5/16's. My 280 tank has a bigger supply so the G3 is it but on the 240 it's 5/16's and the G2 fit like a mother's hug, lovingly tight!
Last reply by siteunseen, -
- 9 replies
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My past experience has been with British car SUs so that may be confusing me. I acquired my 1972 Z a few months ago and have been trying to fix several things the PO did not fix. One is the front carb is causing the first three plugs to become black and gummed up. When I clean the plugs they are black again after about 100 miles. The back plugs are a fine light grey color. In the past my British cars were leaned out by tightening the jet up to the needle. In all the three repair manuals I have for the Datsun, on carbs they focus on the air adjustments. With a Unisync I see both carbs are drawing the same amount of air so I think that adjustment is okay. When I reach…
Last reply by madkaw, -
Where to buy... 1 2
by 3ryce- 12 replies
- 2.8k views
Where would i buy a flow meter for the su carbs? ive searched the internet and have come up with little to nothing helpful. If someone could give me a link or point me in the right direction that would be helpful.
Last reply by 3ryce, -
I am at my wit's end on my racecar. I cannot get my SU fluel levels to set right. Both bowls are 5mm low no matter what I do to the floats, valves, or pressure. I've tried everything I can think of, but I am now out of time. I leave for a race on Thursday afternoon and I have no confidence that I will get it to run right. I'm looking to borrow a set of known good SU carbs that I can have overnighted to me right away. I'd have them for about 1 week. After my race, I plan to send mine to ZT if I can't solve the problem, but for now, I need something that works. I just built a 2.8" 9.5:1 motor with a mild cam that should make about 175 RWHP, but it won't do me any good…
Last reply by madkaw, -
- 0 replies
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Found this online needle profile comparison tool when working on a tr4a yesterday Minty SU Needle Compare-o-rama
Last reply by 240260280z,
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