Forum Fan
Posted 19 November 2013 - 04:59 PM
As one of my metering needles is slightly bent it's probably best that I replace it.
I have aLJ XU-1, 202 with tripple 175 strombergs with 6F needles, apart from extractors and head work I don't know what else has been done to the internals of the engine above XU-1 spec.
Do I stick with the 6F needles or change the size, what size would be best?
In what way is the 6F needle differ from the standard XU-1 6D needle, is it richer, leaner?
_Agent 34_
Posted 19 November 2013 - 06:24 PM
_Agent 34_
Posted 20 November 2013 - 05:56 PM
here are the needles in a comparison chart. i cannot get the curve to the right , but you will see the needle taper to the left in numbers. it should give you a range in which to work to.
but there is other factors to setting these up and they are;
spring rate
adjusting the main jet
So go easy on the needle purchases prior to using other tuning areas of the carbies.
G
Needles.015.Mk2.pdf 128.82K
63 downloads
_Agent 34_
Posted 21 November 2013 - 03:25 PM
sorry didn't put 6 f will do tonight and re post
_Agent 34_
Posted 22 November 2013 - 05:16 PM
here it is with the 6f,
you cannot see the graph and i may change the screen shot to include the whole range. but
i have tried to turn this into a photo so i can show in the screen but it's just not happening. you can see by the needle diameter in size where different needles give more or less fuel as they go along the shank.
At least it will give you a base setting for the needle as you originally asked for.
G
Needles.015.Mkv3.pdf 128.88K
26 downloads
_Agent 34_
Posted 22 November 2013 - 05:38 PM
here it is with the 6f,
you cannot see the graph and i may change the screen shot to include the whole range. but
i have tried to turn this into a photo so i can show in the screen but it's just not happening. you can see by the needle diameter in size where different needles give more or less fuel as they go along the shank.
At least it will give you a base setting for the needle as you originally asked for.
further note, if you look at the taper dimensions of the 6f , it's a lot fatter in diameter which means leaner at WOT. for a hotty 6j is the one you want as it's taper is down to 514. if you compare this to the 6d.
so @ wot
6e- 612
6d- 593
6h- 572
6f- 544
6j- 514
At the end of the day, it's where you need the fuel as apposed to where you don't.
I hope that this has given you some idea where to go with these carbies. having said this spring rate eg , the spring you are running will effect the rise of the needle as well. SO don't do 2 (two ) things at once ie change the spring rate and the needle.
buy a softer set of springs first, but when you do , buy a new set of diaphragms (3) it will cost you not much ( faber at lakember) and change the springs, just changing the springs will give you some advantage in the needle rise VS vacuum , which inturn will seem like the needle is thinner EG at a earlier throttle response Vs rise of slide - eg simple terms MORE FUEL EARLIER as the slide rises faster, thus the needle is at a thinner part of the shank. will not help WOT though this trick
i'd go the spring change its cheaper than needles. but have a look to see where you are chasing the power and then select the needles to go in the right direction.
I'm going to have a lie down now, I'm exhausted
G
Needles.015.Mkv3.pdf 128.88K
21 downloads
Edited by Agent 34, 22 November 2013 - 05:42 PM.
Forum Fan
Posted 24 November 2013 - 01:57 PM
Awesome work. Thanks for that Grant.
Do you know what size needles the 73 Bathurst cars come out with?
Scrivet Counter
Posted 24 November 2013 - 02:12 PM
Awesome work. Thanks for that Grant.
Do you know what size needles the 73 Bathurst cars come out with?
6D, the same as all 202 XU1.
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