240Z240Z240Z

1972 Float Adjustment ...

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    57 minutes ago, jalexquijano said:

    Just noticed that the fuel  pressure even with the new pump is 3 psi when the former one when installed Brand new measured 4.2 psi. Something must  be limiting the fuel pressure even though you argue that 3 psi is enough. Another thing i have noticed is that the engine does crank at 2.5 turns clockwise but  will not hold it for many seconds if i dont open them to 3 turns clockwise on both. I thought that if the engine does not keep up to 2.5 turns without the choke on, something is wrong

    I do not understand why you obsess over this fuel pressure. IT IS NOT THE ISSUE! I have been working on cars for close to 40 years. The issue is in the carb tuning somewhere

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    @Bruce Palmer 

    What is your recommended process for dealing with needle alignment on the three screw 72 carbs when the alignment cones have been sheared off? Is that addressed in your instructions or your video? I thought I had seen some documentation about how to handle this in the past, but I can't put my fingers on it.

    I mean, I know what I would do, but for someone who doesn't understand the issue... What do you guys recommend?20180217_172214.jpg

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    43 minutes ago, Captain Obvious said:

    @Bruce Palmer 

    What is your recommended process for dealing with needle alignment on the three screw 72 carbs when the alignment cones have been sheared off? Is that addressed in your instructions or your video? I thought I had seen some documentation about how to handle this in the past, but I can't put my fingers on it.

    I mean, I know what I would do, but for someone who doesn't understand the issue... What do you guys recommend?20180217_172214.jpg

    With the piston in and dome in place start running the screws down unformly while lifting the piston with a finger and allowing it to drop. If you are cattywompis and the needle is binding, back the screws off a smidge and nurse the dome sideways until it  (the needle) drops freely. Continue until screws are tight and the needle drops cleanly into the orifice...... Do not under penalty of death, adjust your floats during this operation...... Now that's funny I don't care who you are!!

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    51 minutes ago, Bruce Palmer said:

    With the piston in and dome in place start running the screws down unformly while lifting the piston with a finger and allowing it to drop. If you are cattywompis and the needle is binding, back the screws off a smidge and nurse the dome sideways until it  (the needle) drops freely. Continue until screws are tight and the needle drops cleanly into the orifice...... Do not under penalty of death, adjust your floats during this operation...... Now that's funny I don't care who you are!!

    I'm not sure how well that procedure would translate to other languages, or how much sense it would make to someone who's native language is not English.

    You might be about to find out...   LOL

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    1 hour ago, Bruce Palmer said:

    With the piston in and dome in place start running the screws down unformly while lifting the piston with a finger and allowing it to drop. If you are cattywompis and the needle is binding, back the screws off a smidge and nurse the dome sideways until it  (the needle) drops freely. Continue until screws are tight and the needle drops cleanly into the orifice...... Do not under penalty of death, adjust your floats during this operation...... Now that's funny I don't care who you are!!

    Thanks for your kind advice. I might have screwed the float level either on the front or rear carb as the engine still backfires at the carbs intakes at 3.5 turns clockwise. I am not certain of the history of the needle valves and maybe they are not in the correct working order. 

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    Doesn't seem like needle valves would be causing the problem -- there are adjustments built into the carbs that can compensate for minor variance. Nice to have fresh parts for a thorough rebuild, but if the needle action feels smooth and even for both, cross them off the list and go back to the usual suspects.

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    1 hour ago, David F said:

    Timing? Advance a little and see how she responds

    Ill try that tomorrow. 4 hours of setting front and rear carb floats to the correct fuel level. If i bend the tangs more fuel will spill from the lid air inlets.

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    I experienced ocassional fuel bowl overflow.  I attributed the issue to less than optimal float tang geometry.  The modern valve stem design does not glide on the tang as easily as the original design as has been said in this thread previously.  My solution was to remove the sealing washers from the base of the fuel valve body to lid/inlet port.   Once I did that, tang to valve geometry is improved and issue went away.

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    Well i set them at the level shown. All plugs are fouled and car misfires as i start to accelerate. I'll replace all spark plugs with a new set and test the car to see if the misfire and stumbling goes away.

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    On 2/16/2018 at 8:21 AM, David F said:

    Not sure what you are talking about, so I think not.  needles look like any other to me.

    You answered my question from earlier, thanks.

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    47 minutes ago, David F said:

    I experienced ocassional fuel bowl overflow.  I attributed the issue to less than optimal float tang geometry.  The modern valve stem design does not glide on the tang as easily as the original design as has been said in this thread previously.  My solution was to remove the sealing washers from the base of the fuel valve body to lid/inlet port.   Once I did that, tang to valve geometry is improved and issue went away.

     

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    Im reall concerned on the difference on the reading of the psi of the former pump vs this new one which is the same model.  My mechanic did installed a  restrictor after the fuel filter before the carbs. Should i remove it? Its the bronze color one between the clips.

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    Edited by jalexquijano

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    1 hour ago, siteunseen said:

    That's a reducer not a restrictor, for a step down on hose size, it won't affect the PSI.

    Are these fuel levels on the front and rear carb floats okay?

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    1 hour ago, jalexquijano said:

    Are these fuel levels on the front and rear carb floats okay?

    I know you are frustrated, but I'm not sure anyone is going to be able (or willing) to say your fuel levels are okay based on a picture of the tubing fluid level.

    I personally think you should give up on the sight glass method you are using, and try something else. or at least check your levels with this method and see if you are way off base.

     

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    The problem is this diagram shows the level with the float sitting in the fuel, which would bring it further up than it would be when the lid is off.

    This is why the method i used of 10 turns down of the nozzle checks this... as that would equal the 1cm down shown on the right side.  Use a flashlight to check the fluids position on top of the nozzle.

     

    See these references:

    http://datsunzgarage.com/engine/index.htm

    Quote

    HOWEVER: Even though adjusting the floatbowl levels to 23mm down is a factory setting, it doesn't guarantee that the fuel levels in the carbs are the same.

    THE TRICK: 
    I did some measuring with a straightedge and found that on my 4-screw SUs a 23mm fuel level in the float bowl corresponds to exactly 1 centimeter (10 millimeters) below the fuel nozzle "ledge" in the carb. But how do you see to measure fuel 1 centimeter down inside the fuel ozzle? See below. 

    - Remove the dome and main piston from each carb so you can look down the tip of both fuel nozzles. 
    - Screw each mixture nut exactly 10 turns down from fully up. Each full turn drops the nozzle tip 1 mm, so 10 turns puts the tip of the fuel nozzle 10 mm (1cm) down....which happens to be the 23mm float bowl level. 
    - Then look down the tip of each fuel nozzle and adjust each float to set the gas level at the fuel nozzle tip. 

    I ended up taking mine to 9 turns down and set the fuel at the meniscus of the tip. Then when I went to 10 turns the fuel was exactly at the tip. A bit of a juggling act but after a few minutes you will get the hang of it. When you get them to match it's a great feeling.

    NOTE #1: if your mixture nut won't go down more than a few turns, it's because the factory "stopper" next to the nut is still in place. Unless originality is a concern, you can permenantly remove both stoppers from the bottom of the carb. 

    NOTE#2: if the fuel level is too high and overflows the nozzle tip, you will need to drain each float bowl a bit before starting again.

    The result was a lower, more solid idle and less choke needed at startup. I get no stumbling off idle and part-throttle acceleration is smoother, acceleration more powerful. Cruising on the interstate requires a lighter touch on the accelerator. Interesting. 

       

      Edited by DaveR
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      So, all this talk about fuel level made me go recheck mine.  Especially since I set the rear carb the same as the front using the clear tube method.  Removing the pistons and looking at the top of the fuel relative to top of nozzle, the front was perfect and the rear was way low.  So, working on the rear, I set the float so that it was about 1/8” from hitting the cover when inverted.  Rechecked fuel level and still not even close (ie 1/16” from top of nozzle).  Turns out the tang needed to be bent so that float hit top of lid, when inverted.  But, this is okay as fuel shut off occurs prior to float hitting lid.  Now all is good, both fuel levels set to 1/16” down on 2.5 turns.  Fine tune required leaning front and enriching rear...no more than .5 turns for each.  I am hoping cold start is vastly improved.  

      2/26/18 update:  Cold start is vastly improved.  But, I will need to wait until the temps are in the 30's to know for sure.  Also, engine "bucking" when cold and under load has been eliminated.  Rear carb was WAY too lean...explains alot.

      Edited by David F
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      3 hours ago, jalexquijano said:

      Are these fuel levels on the front and rear carb floats okay

      Can't verify the fuel level like that. You need to pull the tubes 2 or 3 inches more through the wire clips that hold them in place, so you have more slack. Then you can hold them right against the side of the bowl and make a horizontal line on the bowl with a pencil, right in line with the gas in the tube. Then get your micrometer and measure from the bottom of the lid to the line you drew. Write down the millimeters and then do the other one. 25 mm front / 21 mm rear down from the lid is correct.

      I also want to check mine with the nozzle method. My car is raked up in the front since I removed the smog pump and swapped the stock brass radiator for an aluminum one. Beat-up stock bumper is also replaced with carbon fiber one. I did some measurements and calculations to get the front/rear carb  fuel level difference correct with the sightglasses, considering the "gasser" rake and the slope of the parking spot, but I think using the nozzle method with the car on a level spot in the parking lot will give better result.

      Nice thing about the sightglasses though, you can leave them hooked up temporarily while idling or driving the car, so you can check that the valves are opening and closing correctly.

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      1 hour ago, Stanley said:

      Can't verify the fuel level like that. You need to pull the tubes 2 or 3 inches more through the wire clips that hold them in place, so you have more slack. Then you can hold them right against the side of the bowl and make a horizontal line on the bowl with a pencil, right in line with the gas in the tube. Then get your micrometer and measure from the bottom of the lid to the line you drew. Write down the millimeters and then do the other one. 25 mm front / 21 mm rear down from the lid is correct.

      I also want to check mine with the nozzle method. My car is raked up in the front since I removed the smog pump and swapped the stock brass radiator for an aluminum one. Beat-up stock bumper is also replaced with carbon fiber one. I did some measurements and calculations to get the front/rear carb  fuel level difference correct with the sightglasses, considering the "gasser" rake and the slope of the parking spot, but I think using the nozzle method with the car on a level spot in the parking lot will give better result.

      Nice thing about the sightglasses though, you can leave them hooked up temporarily while idling or driving the car, so you can check that the valves are opening and closing correctly.

      23  /21 mm from the bottom of the float lid?

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      Many of the methods discussed will get a car running fairly well but in my opinion, the 10 turn method described in multiple posts by @DaveR is your best path to success. There are other factors too, getting the needle aligned, getting the pistons dropping with the right amount of dampening fluid, synchronizing, reading plugs or colortune, etc, etc. But, in my experience there is no better way to get the floats adjusted right than the way DaveR explained....quite well. It is still tedious. You have to turn over the engine, watch the top of the nozzle hole at 10 turns down, pull the float caps, bend and shape the tabs....over and over. The difference though in the 10 turn method and the methods that require you to measure the float height in relation to the float lid or the distance the fuel settles in a clear tube (of which there are differing opinions on what the real measurement is) is accuracy. Once you get the fuel level to settle at the top (but not over) of the nozzle hole at 10 turns down, you are perfect.

      My 2 cents....

      J

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      Can you describe the 10 turns clockwise method precisely? I guess i will need to go through this method in order to get the 23 mm level or wouldnt it be the same if i open both float lids and dip in a caliper to determine how much fuel is in each bowl without cranking the engine then i will know how much i have to bend the tang.

      Edited by jalexquijano

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      16 hours ago, jalexquijano said:

      23  /21 mm from the bottom of the float lid?

      No, 25 mm down, front, and 21 mm down rear. There's supposed to be 4 mm difference between the front and rear. I'm not making it up. It's in the Nissan tech bulletin that I posted couple of days ago. The measurements in the bulletin refer to dimension from bottom of lid to top of float but if you do the math (addition/subtraction) you come up with 25/21. Jonathan Russell posted the bulletin originally on the parallel thread. Suggested reading if you're setting the floats.

      (25+21) / 2=23 mm so the corrected numbers in the bulletin average up to 23 mm. Did you measure the fuel levels like I suggested? It's super easy. What numbers did you get ?

      7 hours ago, jalexquijano said:

      wouldnt it be the same if i open both float lids and dip in a caliper to determine how much fuel is in each bowl without cranking the engine then i will know how much i have to bend the tang.

      Good Idea if you can remove the lids without letting some gas out, which isn't easy. Also, the float will displace some gas though so you'd need to mic it twice, once with the float in place and once with it removed to measure the difference. Suppose the difference is 2 mm (don't go by that - measure the difference !). Then the target would be 27 mm front and 23 mm rear. Don't get any gas on those plastic calipers, take the measurement with the other end.  When you're done, at least check it with the nozzle method.

       

      Edited by Stanley

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      Plug 5 (rear carb) and plugs 2 and 3 (front carb). Idle mixture knobs both at 4 turns clockwise. Car gets stuck on 4 to 5k rpm. Needs more fuel at high rpm. Maybe wrong  float adjustment.

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