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MG Midget and Sprite Technical - Choosing the right needles

Hi

My 1310 engine is running on when I turn it off, you know what I mean! I suspect that it may be down to needle choice for the SUs so I would be grateful to hear what needles you are using and your engine spec.

So..

1310cc, 9.5 CR
266 cam
Ported head
Aldon Yellow dissy, set to 8/9 degrees at tickover without the Vaccum pipe connected
Standard SUs with K&N.

I fitted AH2 needles and red springs, having tried to interpret the Vizard book but I am not sure these are right! I know each engine is different and a RR is the answer, but before I do that I would like to hear your spec's and needle choices to get me a bit closer! The tickover is now set quite low which helps, but it is very engine temp dependant, so if she is hot, it is bad, when the engine is cooler, it isn't such a problem. Any ideas chaps?

Thanks

Robin
Robin Cohen

Robin,

Try this program to give you a guide for needle selection:

http://www.winsu.co.uk/

Don't know whether it still does, but it used to limit you to 10 'goes' without needing to pay for it.

With an Aldon Yellow, the timing needs to be set at 32/34° at 4,000 rpm+ (i.e. maximum advance), which usually results in a 15° advance at around 900/1000 rpm tickover.

A retarded ignition will cause it to run hotter, thus more prone to run-on, as will a weaker mixture.

Are you running on unleaded? This burns slightly slower than leaded, so needs all the advance that is available.
Richard Wale

Robin, take trip to Janspeed Rolling road as they Burlen's next door, so a odd size needle isnt a problem
K Harris

Needle might be ~right - I used one on 10:1 CR BV head and 276; try richening one flat and see if it's better.

Easy to check timing - should be around 7 deg BTDC static...

A
Anthony Cutler

Hi,

Never like bringing the subject of needles up, but as its been raised, would anyone mind if I asked a quick question??

The car I have has a fast road cam (kent), gasflowed cylinder head, performance exhaust and a 5 speed box. As I would expect, idle is a little awful, but I was recommended to change the needles when I had the carbd rebuilt (twin SUs, HS4s)

What would be the best needles? I cant make hide nor hair of the programmes being from the fuel injected era. Please help....Ingrid keeps stalling at the traffic lights!!!

Cheers!

BC
B Cavagan

Hi Robin, what is your idle speed?
Shawn

BC, its quite literally an impossible question to answer. WinSU is the best program to get an estimate and to get a car running. But post serious mods such as cams etc a rolling road really IS the only way of getting near optimum.

I've heard and agree with that on any given set up:

50% of needles would be aweful and undruvable
30% of needles would work but not cleanly through the rev range.
10% of needles would be good fine and would habe the car running 'normally'
5% of needles would be 'good' and a noticable gains would be seen
5% of needles could be considered optimum and would give good fuel economy combined with excellent smooth performance.

Hunting for one of the latter is quite a mission.
Nick

Cheers Nick,

would I need to get a set of needles and take them to a rolling road? Or would they have a set to try?

Any ideas where a good rolling road is around he north east??

BC
B Cavagan

BC

I know its a bit of a trek for you but I would recommend Peter Burgess in Alfreton. He will have a good selection of needles and even alters standard ones to get that extra little tweek.

Carl
C Bintcliffe

Thanks Carl, which county is that in?

BC
B Cavagan

Derby..
David Smith

Shawn

Idle speed is around 800. However, I've just realised that the timing marks on the pulley are about 5 degrees out (having put measured the TDC through the plug hole) so my timing was a lot more retarded than I realised. Richard mentioned earlier that retarded engines run hotter (can you confirm that is correct?)..in which case I may have found the answer.

I actually think that my needles are not too far out as the car runs nicely, smoothly etc..certainly a pleasure to drive!

Rolling roads..just choose carefully. They will all take your money, most won't have a good selection of needles so you can either hope that they know enough to buy the right one and hold onto your car for a few days, or likely you'll get what they do have or their best guess, assuming they won't buy lots of profiles to try..or even worse you've just spent your hard earned having your timing and mixture adjusted! A good RR is great, just choose one that you know has needles in stock or will get a selection in! How do I know..Caterham on carbs..RR in Chesterfield..wouldn't take my wheelbarrow to the cowboy to tune..Pitsopt in Brize Norton..top bloke, top job!
Robin Cohen

my first RR will be at peter burgess. Theres no where in the NE that I would trust to do the job. Although there is a place in malton North yorks that gets a mention every now and again but i forget the name.
Nick

I put my own timing marks on using a vernier timing wheel, and measuring before and after the dwell period at tdc. Mine only shows exact tdc, so I have to use a timing light with adjustable advance. mine runs on because the idle is at 1100. If not, it tries to shake the bonnet off. I have already had 2 bonnet hinges crack. A good rolling road here would probably file your existing needles if they did not have them stock.
Shawn

Peter Burgess's rolling road gets my vote every time and as Shawn says, when any needle modifying needs doing he will change the profile


He made Lara twice the car

Bill

So much easier with a big single SU; file the needle until it's the right part-number...

A
Anthony

Yep!
Nick

Thanks for all the comments. I would point out that whilst every shed in the world is filled with MG owners, cheerfully filing away at their needles..it is a one way ride to richen the mixture and won't help if you are running too rich in places already..unless you solder the needles as well!
Robin Cohen

This thread was discussed between 28/07/2008 and 30/07/2008

MG Midget and Sprite Technical index

This thread is from the archive. The Live MG Midget and Sprite Technical BBS is active now.