1 1/2 SU float height adjust

[davidmuir]

Hi, Got a 'pair' of 1 1/2 SUs in bits for overhaul. How is the float height adjusted on carb- have nylon floats with no metal lever? Nylon float bears directly onto float needle.
Thanks

[Allen Brzeczek]

I have fitted a pair, HS4's, and use them on my own car. I am not aware that there is any means of adjusting the fuel level with the all plastic floats but made the assumption that so long as the floats were in good condition, with no signs of wear on the bearing surface with the valve and moved freely on the pivot that fuel level achieved would automatically be as intended and as originally factory set.

However, I did replace the complete valve assemblies to those where the valve pin has better seating and spring loading onto the float.

Been in use some 4 years now in conjunction with a Facet fuel pump and as such I have had no issues or problems whatsoever.

[davidmuir]

I'll make that same assumption Allen!

[1071 S]

Pretty sure there are little washers/spacers that allow you to adjust the height of the needle/little pointy bit that seals off the jet... (been aaaages since I had to adjust my HS4s)...... or maybe they adjust the location of the seat of the jet???

Cheers, Ian

[65MK1S]

I have fitted a pair, HS4's, and use them on my own car. I am not aware that there is any means of adjusting the fuel level with the all plastic floats but made the assumption that so long as the floats were in good condition, with no signs of wear on the bearing surface with the valve and moved freely on the pivot that fuel level achieved would automatically be as intended and as originally factory set.

However, I did replace the complete valve assemblies to those where the valve pin has better seating and spring loading onto the float.

Been in use some 4 years now in conjunction with a Facet fuel pump and as such I have had no issues or problems whatsoever.

Not trying to hyjack the thread, but what needles are you using in your HS4's. I need a starting point for
my 1283 engine. The existing needles are AAL's and are very rich
Thanks
Kent

[TECH396]

Many years ago the "SU" brand needle and seat assembly came with different thickness washers to be used under the seat where they thread into the cover. This is how I adjusted mine. A thick washer to lower the level or a thin one to raise it.

[davidmuir]

Existing needles in mine are AARs-pretty rich, may need to alter those.
No washers of any size under the float needle assy. and the float is still 'high' going by the manuals (admittedly the measurements are for the 'metal tank type float')

[TECH396]

If the float/fuel level is high without washers under the seat, you can add washers to lower the level.
As a side note.
An old school way of checking fuel level is to remove the dashpot and piston assy. & blow a quick blast of air from your cheeks, quickly & directly down on the jet assy. If the fuel level is correct, you'll notice the fuel pop up then lower out of sight very quickly. It's a hard technique to describe but it's a perfect way to check the level quickly without removing the float chamber covers. Don't try compressed air !
.

No washers of any size under the float needle assy. and the float is still 'high'

[Allen Brzeczek]

Interesting to hear about the washers but I can understand how this would work.

In answer to your question I am using AAM needles and red springs

[Aussie Bill B]

Pretty sure there are little washers/spacers that allow you to adjust the height of the needle/little pointy bit that seals off the jet... (been aaaages since I had to adjust my HS4s)...... or maybe they adjust the location of the seat of the jet???

Cheers, Ian

Ian's and TECH396's comments are my understanding too. As the whole mechanism wears, the errors add up to the float sitting higher up in the chamber and giving a higher fuel level in the jet.
The little spacer washers sit under the seat (of the needle and seat) where it screws into the float bowl, with the effect of lowering the shut off point when the needle closes off flow to the bowl and giving a lower fuel level in the jet.

[underkut]

I recently rebuilt and installed a set of hs4's from a 1800 marina tc. The floats leaked straight away although I changed the angle. With no easy adjustment AND ethical I bought a pair of black stay up floats , that had the little metal tags ,so I could easily adjust them. Problem sorted and hopefully averted a future issue. I cannot recall from memory what the needles were and although I changed them they were almost right. This is for a 1400 with md286 cam.
Cheers