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| Needle for 1.5SU - 1275 https://www.ausmini.com/forums/viewtopic.php?f=2&t=99830 |
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| Author: | 3ug3 [ Wed Apr 08, 2020 9:25 pm ] |
| Post subject: | Needle for 1.5SU - 1275 |
Sorry. It’s one of those endless questions, but thought I’d chuck it out there again. I was looking at an SU needle to suit the following: - Stock 1275cc from a Morris 1100s. - 12G940 head - 1.5” SU on minispares intake manifold - [edit] standard metal air filter housing - 1.75” 3to1 extractors (the 3 joins up above the diff - 1.75” all the way through to standard RC40 side exit My current needle is bent and I’m trying to roll it out straight again. So I though I might look into something that suits this current setup. It’s a standard road setup. Nothing special. Not looking for more power or anything... just a good all round needle. Wide torque curve would be nice. Lots of hills in Brisbane. Also, there’s a spring on top of the needle... what on earth is going on there? When I pulled the piston off, I could just wobble the needle... que? Happy shiny minis people!!! Sent from my iPhone using Tapatalk |
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| Author: | Alexw [ Thu Apr 09, 2020 12:18 am ] |
| Post subject: | Re: Needle for 1.5SU - 1275 |
Standard cam? The "hanging" needle is an improvement that reduces the wear on the side of the needle. The profile of the side of the needle is the mixture curve, so you don't want that wearing. Sent from my Pixel 3a XL using Tapatalk |
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| Author: | drmini in aust [ Thu Apr 09, 2020 6:16 am ] |
| Post subject: | Re: Needle for 1.5SU - 1275 |
I found a CP4 works fine with a lynx ramflo filter and your manifold. However this is a fixed needle. I wouldn't call the floating needle an improvement, they wear themselves and the jet too. |
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| Author: | 3ug3 [ Thu Apr 09, 2020 9:28 am ] |
| Post subject: | Needle for 1.5SU - 1275 |
I’m not sure about the cam. I assume it’s also stock. Forgot... the air filter is standard 1.5SU metal one. I’ll update the list at the top. Sent from my iPhone using Tapatalk |
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| Author: | Bill B [ Thu Apr 09, 2020 10:43 am ] |
| Post subject: | Re: Needle for 1.5SU - 1275 |
The spring-loaded needle was introduced to offer more consistent metering of fuel. If the needle rested against the side of the jet, the area remaining to allow fuel past was more accurate/consistent than having the needle sitting in the centre of the jet and not touching the jet sides, as the early SUs did. New SUs come with the spring needle arrangement. I don't understand the argument at all, but as Drmini says, they are known for rapid wearing of needle and jet. I run CP4 needles in twin HS4s on a standard S motor. The needle for a single carb is usually not very different to a twin setup. The spring needle set up can be converted back to a fixed needle, which offers a larger range of needle profiles. You will need WZX2003 to fit the needle to the newer piston; but you also need WZX1341 the jet bearing kit for fixed needles. |
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| Author: | timmy201 [ Thu Apr 09, 2020 10:45 am ] |
| Post subject: | Re: Needle for 1.5SU - 1275 |
The 1275 GT (factory single HS4) in the UK had an AAR swinging/floating needle and red spring. What needle do you have now? Some factory examples: https://www.7ent.com/pages/articles-tec ... eedle.html |
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| Author: | IndigoBlueCooperS [ Thu Apr 09, 2020 11:05 am ] |
| Post subject: | Re: Needle for 1.5SU - 1275 |
I think you may find the main carby body is different between the fixed and floating needles. The fixed needle body has a larger hole where the brass bit (female needle receptacle) goes into, to allow it be moved around to centre the needle. This hole is smaller on the floating needle as you don't need the flexibility to centre the jet. This was on HS6's, from a Marina and Austin 1800. May not be an issue with the HS4. |
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| Author: | Bill B [ Thu Apr 09, 2020 11:32 am ] |
| Post subject: | Re: Needle for 1.5SU - 1275 |
IndigoBlueCooperS wrote: I think you may find the main carby body is different between the fixed and floating needles. The fixed needle body has a larger hole where the brass bit (female needle receptacle) goes into, to allow it be moved around to centre the needle. This hole is smaller on the floating needle as you don't need the flexibility to centre the jet. This was on HS6's, from a Marina and Austin 1800. May not be an issue with the HS4. I have converted a new set of HS4s from swing to fixed using the jet bearing kit which has a different sleeve to allow the jet bearing to be adjustable for centring. http://www.minispares.com/product/Class ... o%20search |
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| Author: | 3ug3 [ Thu Apr 09, 2020 11:45 am ] |
| Post subject: | Re: Needle for 1.5SU - 1275 |
timmy201 wrote: The 1275 GT (factory single HS4) in the UK had an AAR swinging/floating needle and red spring. What needle do you have now? Some factory examples: https://www.7ent.com/pages/articles-tec ... eedle.html Thanks. I was looking at that site. I've got an ADF. I know it doesn't make that much difference in a road car. I just wanted to research if my bent needle was ok. I'll try the CP4. |
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| Author: | timmy201 [ Thu Apr 09, 2020 12:06 pm ] |
| Post subject: | Re: Needle for 1.5SU - 1275 |
If you change to the fixed needle you’ll need the conversion kit like Bill has mentioned Here is AAR v CP4 Attachment: 1F650872-AB9C-4015-8915-691A1D21EBCB.jpeg
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| Author: | Bill B [ Thu Apr 09, 2020 2:07 pm ] |
| Post subject: | Re: Needle for 1.5SU - 1275 |
3ug3 wrote: timmy201 wrote: The 1275 GT (factory single HS4) in the UK had an AAR swinging/floating needle and red spring. What needle do you have now? Some factory examples: https://www.7ent.com/pages/articles-tec ... eedle.html Thanks. I was looking at that site. I've got an ADF. I know it doesn't make that much difference in a road car. I just wanted to research if my bent needle was ok. I'll try the CP4. Is your "bent needle" damaged or just leaning over like intended? I have 2 spring needles from the carbs I converted. They are AAK, if that is close to suitable. Timmy might be able to find what they might have been intended for and/or compare with AAR on his neat little comparison charts. Even for a road car, it is important to be close to correct. |
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| Author: | timmy201 [ Thu Apr 09, 2020 2:44 pm ] |
| Post subject: | Re: Needle for 1.5SU - 1275 |
This is the site, there are a couple of others like mintylamb https://www.classicminidiy.com/technical/needles |
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| Author: | drmini in aust [ Thu Apr 09, 2020 8:30 pm ] |
| Post subject: | Re: Needle for 1.5SU - 1275 |
Re that graph, the last 3 points on the CP4 are wrong. It's just the needle is shorter? I believe. |
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| Author: | Bill B [ Thu Apr 09, 2020 10:44 pm ] |
| Post subject: | Re: Needle for 1.5SU - 1275 |
One of the SU needle books I looked at list AAF and AAR (and many others) with 16 listed points of measurement at 1/8inch spacing. CP4 only lists 13 points of measurement like many other needles intended for H2 and HS2. The graph had to go to a default setting for the missing 3 measurements giving an odd curve. |
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