S.U. Needles

[roybr]

Having recently returned to S.U. carbs, after many years,and in the process of deciding to re-build mine, I remember working on a Marina T.C. with twin S.U.s. and I recall that the needles were "spring" fitted, as opposed to rigid, in the pistons.I think the theory was that the needles were always in the same position, not necessary central in the jet,so the carbs stayed in tune better/longer.

Question is,would it be worth doing this to H4's, could it be done? Was it an improvement back then, OR,was it not worth doing in the first place. Just a thought.

Happy New Year to all.

[Chris Hubball]

Having recently returned to S.U. carbs, after many years,and in the process of deciding to re-build mine, I remember working on a Marina T.C. with twin S.U.s. and I recall that the needles were "spring" fitted, as opposed to rigid, in the pistons.I think the theory was that the needles were always in the same position, not necessary central in the jet,so the carbs stayed in tune better/longer.

Question is,would it be worth doing this to H4's, could it be done? Was it an improvement back then, OR,was it not worth doing in the first place. Just a thought.

Happy New Year to all.

 

[Chris Hubball]

Hi Roy

 

I worked at SU for over 30 years and the spring needle fixing called a swinging needle was intended to help improve exaust immissions. To convert your carbs you would need new Suction Chambers and pistons as the needle fixing is totally different added to which the needle itself is longer and would need a collar fitting all of which would have to be especialy made if you could find someone with the knowhow and equipment.All this would involve a lot off hassel and money and would be of no benefit to our type of car.

 

Cheers

 

Chris Hubball

[roybr]

Hi,Chris,

thanks for your concise reply, think I'll be re-building them as they should be.

[Peter Cobbold]

Hi Roy

 

I worked at SU for over 30 years and the spring needle fixing called a swinging needle was intended to help improve exaust immissions. To convert your carbs you would need new Suction Chambers and pistons as the needle fixing is totally different added to which the needle itself is longer and would need a collar fitting all of which would have to be especialy made if you could find someone with the knowhow and equipment.All this would involve a lot off hassel and money and would be of no benefit to our type of car.

 

Cheers

 

Chris Hubball

 

 

 

Chris,

I have been searching for flow bench data on SUs for years (on and off), particularly manometer measurements of the venturi

depression in the jet area. Can you suggest where I should be looking, who I should ask? I am trying to modulate cruise mixture by adjusting the pressure of air in the floar chamber, similar to SU's gadget they made ( when?) for supercharged engines.

Peter

Peter

[Chris Hubball]

Chris,

I have been searching for flow bench data on SUs for years (on and off), particularly manometer measurements of the venturi

depression in the jet area. Can you suggest where I should be looking, who I should ask? I am trying to modulate cruise mixture by adjusting the pressure of air in the floar chamber, similar to SU's gadget they made ( when?) for supercharged engines.

Peter

Peter

 

[Chris Hubball]

Hi Peter

Sorry I cannot help you with the information you require.Suggest you contact Burlen Fuel Systems in Salisbury we transfered all our drawings and technical data to them when we closed down in 2003.

 

Regards Chris.

[Peter Cobbold]

Thanks Chris.

 

Burlen are a dead loss, to quote from their contact page:

""Due to extremely high demand we are unfortunately unable to answer emails asking for advice on non-standard applications performance tuning and modifying carburetters or cars.""

 

My modification is distinctly non-standard!!

I'll follow my own path.

 

Peter