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| Carby Issues and Needle Choice for 1 1/2" SU's https://ausmini.com/forums/viewtopic.php?f=2&t=100599 |
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| Author: | Fritzie [ Sat Dec 12, 2020 7:56 pm ] |
| Post subject: | Carby Issues and Needle Choice for 1 1/2" SU's |
I have been having issues trying to tune my carbs lately on my 69"S". They have been running very rich, to the point they are fouling plugs (Champion N9YC) and I can wind the mixture screw up as far as it will go. It still runs and indicates running rich on my colortune plug. I tried dropping the float levels with no change to richness. I had noted that when the mixture screws were fully wound up, the top of the jet was marginally lower (about 0.4mm) than the bush that it sits in. Today I reset my needles to be lower than the usual method of the shoulder being flush with the bottom of the piston. Before I centred the needle, I set the shoulder height of the needle to be flush with the top of the jet. It seems to have done the trick and I can now see a noticeable difference when idling. I can actually get the colortune to show a blue colour set at 6 flats lower than top. Just wondering if anyone else has had similar issues and has had to resort to lowering the jet. Is it a sign of wear in the needle and jets? I am currently running GP needles in my 1 1/2" SU's. From memory I think, they are somewhere between No.7 and BP on SU charts. What needles are used on Police "S"? Regards Fritzie |
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| Author: | gtogreen1969 [ Sat Dec 12, 2020 8:09 pm ] |
| Post subject: | Re: Carby Issues and Needle Choice for 1 1/2" SU's |
CP4 needles with Blue dashpot springs |
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| Author: | pdpsing [ Sun Dec 13, 2020 8:15 am ] |
| Post subject: | Re: Carby Issues and Needle Choice for 1 1/2" SU's |
I run #6 with blue springs on my ex Police S. Similar profile to CP4. Runs really well, starts easily, good idle and power band Sent from my SM-A305YN using Tapatalk |
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| Author: | Fritzie [ Sun Dec 13, 2020 9:35 am ] |
| Post subject: | Re: Carby Issues and Needle Choice for 1 1/2" SU's |
Just checked the Mintylamb site for SU needles. It looks like the GP is the same as a No.6 needle except that station 3, 4 and 5 are richer. Station 4 on the GP needle is signficantly richer. From Station 6 on, it looks like No.6 and GP needles are the same. I think that I might try No.6 needles, hopefully this may improve my richness at idle. Thanks for that Regards Fritzie |
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| Author: | pdpsing [ Sun Dec 13, 2020 1:32 pm ] |
| Post subject: | Re: Carby Issues and Needle Choice for 1 1/2" SU's |
Ran BG needles initially as apparently fitted originally to the STP cars. Couldn't get a satisfactory idle, although heaps of go at higher revs. Found the #6 to be better compromise Sent from my SM-A305YN using Tapatalk |
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| Author: | Ian_B [ Sun Dec 13, 2020 3:18 pm ] |
| Post subject: | Re: Carby Issues and Needle Choice for 1 1/2" SU's |
Yea Calver suggests ABY with 286 style cam . The first little bit of the needle is very critical coming off idle then pour it in . |
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