I'm not sure if it is the same one, but there was a program sometimes called 'haystack' (needle in a haystack, geddit geddit) which was also called SUneedle. It's still available on the net. It run in dos originally, but does run ok on XP. It not only has the needle lists, but it lets to you enter one profile, then displays its dimensions across 12-16 heights, and then lets you type in another profile (say BQ for example) and it will display it, not in terms of outright attributes, but instead it will list the difference in thickness at each of the heights (positive number = leaner than original profile, negative number = richer)
One of the small idiosynchrasies with these needles, is that although you want it thicker or thinner in the mid/high range, it's not the only one to consider. For example if they are markedly different around the thickest/idle range, then you'd have to raise or drop the jet to get the idle right, then it'd be like each measurement 'jumped' a notch, so you are no longer comparing apples to apples. Which is one of the reasons they shit people to tears
What can be good is to take two known needles, lets say for example the needle for twin 1 1/4 SUs in 1275 cooper S trim - red spring and m needle, and the factory rich needle is AH2
-M- 890 855 832 808 785 763 745 726 707 688 669 650 000 000 000 000
AH2 890 850 820 794 770 748 726 704 683 662 640 620 600 000 000 000
Difference 000 -5 -12 -14 -15 -15 -19 -22 -24 -26 -29 -30 99 000 000 000
That's about enough change to go from perhaps around 12.5-12.8ish to 12:1 under load (for argument's sake, not actual figures, but representative of extent of change)
ADF 890 850 822 803 775 746 730 707 685 660 638 615 590 570 550 530
BQ 890 850 820 790 750 725 705 685 662 640 616 594 570 000 000 000
Difference 000 000 -2 -13 -25 -21 -25 -22 -23 -20 -22 -21 -20 -99 -99 -99
Here is your needle compared to a BQ indicative of a similar change.
Here's some needles perhaps worth a look (not an exhaustive list, but some close ones from memory)
From now on only differences from ADF needle will be shown for clarity
ADF 890 850 822 803 775 746 730 707 685 660 638 615 590 570 550 530
BQ 000 000 -2 -13 -25 -21 -25 -22 -23 -20 -22 -21 -20 -99 -99 -99
BP 000 000 -8 -23 -35 -31 -35 -34 -35 -35 -38 -35 -30 -99 -99 -99
BU 10 000 -22 -33 -30 -26 -35 -32 -30 -35 -36 -35 -30 -99 -99 -99
6 000 000 -8 -18 -20 -21 -34 -41 -49 -54 -61 -65 -70 -99 -99 -99
I'd be _really_ surprised if you had to go to #6 needle.
Given just how much you have to pull the choke to improve acceleration *(it should bog down a bit by that much extra enrichment) I'd actually suggest that it might be in need of a stiff enough spring. It _should_ be a red spring given the engine size and carb size, relatively. If it is unclear which spring it is, or if it is old/sagged, then I've probably got a bunch of them, you are welcome to any of them for postage costs. On the same track, I've almost certainly got a BQ needle here too. Just have to dig it up. I got into the habit of stripping any/all SUs I had. Many were stock minis, not much use elsewhere, but sometimes they had odd needles in there. I then wrapped a piece of wide sticky tape around them, and wrote the profile down in permanent marker on the tape, in large easy to read at a glance and from far away imperfect lights etc. Occasionally I've ended up having just the right needle to sort an engine or two here or there.
---
Basically spring choice is simple, you want the piston in the carb to just rise to the top of its travel at peak airflow (which usually = peak hp rpm), If it doesn't you don't get to utilise the entire needle profile to set the a/f curve, and it'll never be particularly tunable. And thus it logically follows that if you have to run a ridiculously light or heavy spring to get that to happen, it's a sure sign that the carb is too large or small for the engine/combo respectively.
On the oil in the dashpot - again simple idea - when airflow increases, it works like a shock absorber (or as they would more accurately be termed) a damper, and slows the rise of the piston. this creates a temporarily higher pressure drop across the jet until the piston reaches the height that = that airflow requirement, and that means it runs a little richer. This is, in effect, the accelerator pump replacement, and it works very well. The thicker the oil, the longer it takes to rise, the longer it stays transiently rich, the more acc pump action. so when you hear people discussing running no oil in them at all (for example) for 'better throttle response' - that's actually not the case. No oil in there and it opens so fast that it'll lean out (a bit like holley vac sec opening too quick) amd it'll have a flat spot, the exact opposite of what you want. So you need SOME type of oil in there. The solution here is again simple. you test it with thick oil (perhaps some 'old engine' type oil (trans fluid is around 5w 30 I seem to recall, and in the last few years dexron - the latest one - is thinner than trans fluid of old, so it's worth noting for use in this app). Anyway, you try it, then try thinner and thinner (you can of course mix sewing machine oil and regular oil, or whatever it takes) until it starts to develop a flat spot as you floor it. And once you find that point, go back one or two 'formula' thicker (most likely 2, just to be sure).Some guys have even experimented with diff oil. IMO if diff oil 'works' and it accelerates better like that, then it's a sign that the spring is almost certainly on the light side, but also that the needle is way lean. I'd _always_ check the spring first, because iwthout a consistent spring with a load within spec, it'll work as well as a labor government initiative (and I reckon that joke would still have meaning in 50 years)
One of the small idiosynchrasies with these needles, is that although you want it thicker or thinner in the mid/high range, it's not the only one to consider. For example if they are markedly different around the thickest/idle range, then you'd have to raise or drop the jet to get the idle right, then it'd be like each measurement 'jumped' a notch, so you are no longer comparing apples to apples. Which is one of the reasons they shit people to tears
What can be good is to take two known needles, lets say for example the needle for twin 1 1/4 SUs in 1275 cooper S trim - red spring and m needle, and the factory rich needle is AH2
-M- 890 855 832 808 785 763 745 726 707 688 669 650 000 000 000 000
AH2 890 850 820 794 770 748 726 704 683 662 640 620 600 000 000 000
Difference 000 -5 -12 -14 -15 -15 -19 -22 -24 -26 -29 -30 99 000 000 000
That's about enough change to go from perhaps around 12.5-12.8ish to 12:1 under load (for argument's sake, not actual figures, but representative of extent of change)
ADF 890 850 822 803 775 746 730 707 685 660 638 615 590 570 550 530
BQ 890 850 820 790 750 725 705 685 662 640 616 594 570 000 000 000
Difference 000 000 -2 -13 -25 -21 -25 -22 -23 -20 -22 -21 -20 -99 -99 -99
Here is your needle compared to a BQ indicative of a similar change.
Here's some needles perhaps worth a look (not an exhaustive list, but some close ones from memory)
From now on only differences from ADF needle will be shown for clarity
ADF 890 850 822 803 775 746 730 707 685 660 638 615 590 570 550 530
BQ 000 000 -2 -13 -25 -21 -25 -22 -23 -20 -22 -21 -20 -99 -99 -99
BP 000 000 -8 -23 -35 -31 -35 -34 -35 -35 -38 -35 -30 -99 -99 -99
BU 10 000 -22 -33 -30 -26 -35 -32 -30 -35 -36 -35 -30 -99 -99 -99
6 000 000 -8 -18 -20 -21 -34 -41 -49 -54 -61 -65 -70 -99 -99 -99
I'd be _really_ surprised if you had to go to #6 needle.
Given just how much you have to pull the choke to improve acceleration *(it should bog down a bit by that much extra enrichment) I'd actually suggest that it might be in need of a stiff enough spring. It _should_ be a red spring given the engine size and carb size, relatively. If it is unclear which spring it is, or if it is old/sagged, then I've probably got a bunch of them, you are welcome to any of them for postage costs. On the same track, I've almost certainly got a BQ needle here too. Just have to dig it up. I got into the habit of stripping any/all SUs I had. Many were stock minis, not much use elsewhere, but sometimes they had odd needles in there. I then wrapped a piece of wide sticky tape around them, and wrote the profile down in permanent marker on the tape, in large easy to read at a glance and from far away imperfect lights etc. Occasionally I've ended up having just the right needle to sort an engine or two here or there.
---
Basically spring choice is simple, you want the piston in the carb to just rise to the top of its travel at peak airflow (which usually = peak hp rpm), If it doesn't you don't get to utilise the entire needle profile to set the a/f curve, and it'll never be particularly tunable. And thus it logically follows that if you have to run a ridiculously light or heavy spring to get that to happen, it's a sure sign that the carb is too large or small for the engine/combo respectively.
On the oil in the dashpot - again simple idea - when airflow increases, it works like a shock absorber (or as they would more accurately be termed) a damper, and slows the rise of the piston. this creates a temporarily higher pressure drop across the jet until the piston reaches the height that = that airflow requirement, and that means it runs a little richer. This is, in effect, the accelerator pump replacement, and it works very well. The thicker the oil, the longer it takes to rise, the longer it stays transiently rich, the more acc pump action. so when you hear people discussing running no oil in them at all (for example) for 'better throttle response' - that's actually not the case. No oil in there and it opens so fast that it'll lean out (a bit like holley vac sec opening too quick) amd it'll have a flat spot, the exact opposite of what you want. So you need SOME type of oil in there. The solution here is again simple. you test it with thick oil (perhaps some 'old engine' type oil (trans fluid is around 5w 30 I seem to recall, and in the last few years dexron - the latest one - is thinner than trans fluid of old, so it's worth noting for use in this app). Anyway, you try it, then try thinner and thinner (you can of course mix sewing machine oil and regular oil, or whatever it takes) until it starts to develop a flat spot as you floor it. And once you find that point, go back one or two 'formula' thicker (most likely 2, just to be sure).Some guys have even experimented with diff oil. IMO if diff oil 'works' and it accelerates better like that, then it's a sign that the spring is almost certainly on the light side, but also that the needle is way lean. I'd _always_ check the spring first, because iwthout a consistent spring with a load within spec, it'll work as well as a labor government initiative (and I reckon that joke would still have meaning in 50 years)
And you are correct yet again 
Comment