11 replies to this topic

[Dusky]

Hi!

 

 

I bought myself some needle collars to convert my fixed needles to the swinging type, but how the (Insert a word here ) do I fit these collars to the needle?

Its a kind of press-fit, but it seems to be hard to do without bending the needle??

 

Any advice? Already tried freezing the needles and putting the collars in boiling water<;

 

thanks

Diego

[Gremlin]

Are they for the right size needle? Is the hole size far different? on different size carbs the gixed needle is a different diameter where it sits in the piston

[Dusky]

Right size of needles ( All for HS2, HS4)

It looks like it will fit when you hammer on it, but that would bend the needle :/

[Gremlin]

Ask the supplier, and if need's must send it back, if he says it'll fit get it in writing he'll provide a new needle if yours bends fitting it. If you do that ^ and your needle is not a unmodified off the shelf measure it carefully at 1/8" incremements all the way down so you could get another one made

[KernowCooper]

Just to help out Dusky Not kowing the definite answer to this but suspecting the Slide assembly has a bigger hole to accept the swing needle collar, I rand Burlen Fuel Systems who make the SU, they confirmed the swing needle collar is indeed bigger and to do the conversion you need new slide and vacuum housing as a matched pair to do the conversion.

[Dusky]

I got the swinging type housing , thats why I want to convert the needles, as I don't know which swinging needle would fit otherwise( vizard advises nr 3 - nr 4) and don't know of any hs4 needle which reassembles the profile

[dklawson]

I could propose a few ways to do what you are suggesting but all involve tools you may not have at your disposal.  Do you have a lathe?  Do you have a milling machine or drill press (pillar drill)?  Do you have soldering equipment?  Do you have accurate measuring equipment (vernier or electronic calipers as a minimum)?

[Dusky]

I do have a pilar drill, soldering equipment and the measuring equipment. Only the lathe is difficult:p

[dklawson]

Look carefully at a swinging needle.  You will note the spring collar is positioned a certain distance from the "shoulder" on the needle body where the taper starts (see the pictures below).  The shoulder on the needle must be positioned the correct distance from the collar.  Measure that distance on a purchased swinging needle.

 

To fit a fixed needle to the collars you bought, hold the straight body of the fixed needle in the drill press with the taper going up inside the chuck (do not clamp on the taper!).  You want to hold the straight part in the chuck leaving enough exposed for you to sand sufficient length down to insert into the collar.  Start the drill and use fine wet/dry sandpaper to slowly reduce the diameter of the exposed fixed jet shoulder until it can just barely be inserted in the collars you bought.  (Measure multiple times and stop when you have a close fit that can be assembled by hand).  This is much easier on a lathe than a drill press.

 

Now insert the modified fixed jet into the collar to match the depth you measured for a purchased swinging needle.  On the open end of the collar (see picture below), solder the two parts together.  Use a small scribe to make some form of sensible engraving on the collar so you will know what the needle assembly is. 

 

This is a lot of work compared to buying the correct swinging needle to match what you want.  Have you visited the Mintylamb web site and worked with its utilities to find the swinging needle to match your fixed needles?

http://www.mintylamb.co.uk/

 

There is also Paul Tegler's Triumph/MG web site that has a lot of SU utilities that can help you match needle profiles.

http://www.teglerize...ledb/index.html

 

 

[carbon]

I got the swinging type housing , thats why I want to convert the needles, as I don't know which swinging needle would fit otherwise( vizard advises nr 3 - nr 4) and don't know of any hs4 needle which reassembles the profile

 

For info, HS4 carb pistons & dashpots can be either swing or fixed needle. Fixed needle HS4s are typically from 60's and early 70's.

[Dusky]

The weard thign is that there is no consistency between Vizard and minimania. Vizard advised NR 3, 4 or even a BG dependign on how good the headwork is.

Then minimania's table of tested needles is a ABM- ABY for a 286 cam. Do swinging needles give leaner results because they're swinging? O.o

[carbon]

The recommended needles for modified engines are just a starting point.

 

If you had a fixed needle carb with an accurately centred jet and a swing needle carb of exactly same needle proflie, then the swing needle might run very marginally richer than the fixed needle, and this would be more noticeable at idle and small throttle openings. This is because the swing needle jet is always touching the side of the jet, while fixed needle is centred, and this affects fuel flow very slightly.

 

But likely to be very marginal difference in practice.