12 replies to this topic

[chris1965mk1]

Afternoon all,

 

I am currently attempting to rebuild my twin su`s picked up last weekend and need some help with needle / spring choice please ?

 

I have found some info online that leads me to believe i need `M` needles like link below

 

http://www.ebay.co.u...GYAAOSwT5tWM9KP

 

My problem is that for these carbs on my 1275cc engine there is also a RICH option and options with springs ?

 

 

Twin HS2 1.25" Engine Size Needle Std. Needle Rich Needle Lean Spring Type 850 EB-GG - - Blue 997 Cooper GZ AH2 EB Red 998 Cooper GY M GG Blue 998 Clubman GX M GG Red 998 Innocenti GY M GG Red 1098 EB-GV D3 D6 Red 970 Cooper S AN H6 EB Red 1071 Cooper S H6 3 EB Red 1275 Cooper S M AH2 EB Red 1275 Innocenti, Bias AAP - - Blue

Bias = Spring loaded needle

Can anyone help me with the differences between the options and what the spring colour has to do with anything ?

 

I will be upgrading the performance of the engine with roller rockers or a fast road cam at some point so does that effect the choice ?

 

Does anything else on the carbs need changing to suit 1275 as the needles inside at the mo are coded GY for 998 cooper !

 

Thanks in advance

[chris1965mk1]

Better link for needle codes

 

http://www.7ent.com/...tor-needle.html

[Dusky]

If you run the car without the upgraded cam etc now it does make a difference. You always need the right needle for your engine spec. The springs are just a part of the calibration, they keep the piston to a cerrain height for a cerrain engine vacuüm.

[chris1965mk1]

If you run the car without the upgraded cam etc now it does make a difference. You always need the right needle for your engine spec. The springs are just a part of the calibration, they keep the piston to a cerrain height for a cerrain engine vacuüm.

Was looking at the Evolution cam on minispares site , so you think to go with the Rich option if i do ? 

[carbon]

Once you have a better idea of the engine spec it may be possible to suggest starting point for needle. But it will only be a guess, as it is affected by air filter, inlet manifold, head specification, cam profile, compression ratio, and exhaust. Typically as you increase the level of tune the motor needs more fuel, and this requires a needle with thinner section.

 

Most people will advise to get it set up by a competent rolling road once the engine is running.

 

The two piston spring types used in the mini twin HS2 carbs are red and blue. Blue runs weaker than red for a given needle profile. There are two types of needles, fixed and swing, and you can tell which type to use from the pistons you have fitted.

[Dusky]

I 'd go for a richer needle than the standaard 1275 needle, not S!but impossible to think of a correct needle without the full head/cam/... spec . :)
Needle and spring combo's are a wiff of magic. Your spring will ideally be fully compressed at peak rpm for example, the harder the engine istuned the stronger the spring is what I tend to see( also what winsu tends to advice, winsu is a software that suggest needles for a given engine spec)

Edited by Dusky, 18 May 2016 - 08:31 AM.

[KernowCooper]

M needles are for a 1275 S spec engine and as yours is standard then your spec is way off for the S Spec standard needle

[chris1965mk1]

My needle is the same type as listed in the Ebay link i posted (fixed type).

I can`t see a standard 1275 option in the needle link ? How can i get the car tuned on a rolling road without needles in the carbs in the first place ? 

I hear what you are saying about the level of performance depicting the needle required but there must be a standard needle available for my A+ 1275cc engine un-tuned with no upgrades and a richer one for if i fit a 266 cam or high lift rockers (i will be doing one of these mods but not both).

As the engine is out of the car i have been advised to upgrade the Cam and leave the Hi-Lift rollers for cost reasons more than anything as Cam will do the same job but for half the price .

Is there a way of working out which needle/spring to purchase based on the Engine size & Cam ratio ?

 

Unfortunately i am a child of the injection generation so Carbs are a bit foreign to me 

 

Thanks again

[chris1965mk1]

M needles are for a 1275 S spec engine and as yours is standard then your spec is way off for the S Spec standard needle

Any idea what needle for the standard spec then ?

 

Cheers

[chris1965mk1]

I 'd go for a richer needle than the standaard 1275 needle, not S!but impossible to think of a correct needle without the full head/cam/... spec . :)
Needle and spring combo's are a wiff of magic. Your spring will ideally be fully compressed at peak rpm for example, the harder the engine istuned the stronger the spring is what I tend to see( also what winsu tends to advice, winsu is a software that suggest needles for a given engine spec)

What is Winsu ? Thanks for the advise 

[Dusky]

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

 :)

 

AN needles were standard on the 1275 sprite if my memory serves me right. That'll be very close to your standard 1275. :)

Edited by Dusky, 18 May 2016 - 03:40 PM.

[KernowCooper]

The problem is no standard 1275 came out with twin 1 1/4s, unless someone here has that setup then its guesswork, I'd not want you to be running to rich and bore wash the engine

[carbon]

My needle is the same type as listed in the Ebay link i posted (fixed type).

I can`t see a standard 1275 option in the needle link ? How can i get the car tuned on a rolling road without needles in the carbs in the first place ? 

I hear what you are saying about the level of performance depicting the needle required but there must be a standard needle available for my A+ 1275cc engine un-tuned with no upgrades and a richer one for if i fit a 266 cam or high lift rockers (i will be doing one of these mods but not both).

As the engine is out of the car i have been advised to upgrade the Cam and leave the Hi-Lift rollers for cost reasons more than anything as Cam will do the same job but for half the price .

Is there a way of working out which needle/spring to purchase based on the Engine size & Cam ratio ?

 

Unfortunately i am a child of the injection generation so Carbs are a bit foreign to me 

 

Thanks again

The MD266 cam in a 1275 works much better when you have valve lift of 8mm or more. It's a good profile but a bit short on lift at the lobe when compared to a lot of the modern fast road cam grinds.

 

If you settle on MD266 with twin HS2s, then PM me once you have built the engine. I can give you some pointers on fixed needle options as a starting point.