Needle for twin HS4s

[Minigman]

I’m running AAK needles in twin HS4s on a 1330 with a good ‘stage 3’ head and a 276 cam.

Seems to be running very rich at idle and low revs before going lean at about 4000rpm when the engine holds back unless I keep my foot buried. Once you get above 4700rpm it seems fine again.

So with a 3.44FD, I can do 60mph or 80mph on the motorway but not much else in between without the annoying stutter.

Any ideas on which profile to try next?

I’ve got a rolling road session booked with Tipton Garage in a couple of weeks so be good to have it closer to perfection before then.

[Daveislandblue66]

This is pretty good for looking up SU needle profiles. You'll need to put AAK in as needle one, and then work through the others to find one that has the sort of profile you need.

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

[Minigman]

This is pretty good for looking up SU needle profiles. You'll need to put AAK in as needle one, and then work through the others to find one that has the sort of profile you need.

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

I’ve just this second been looking at this.

I’ve put most of the Vizard recommended needles for this engine spec and I reckon AAA would do the job nicely assuming more elevated the line on the graph the richer the needle is?

[Charlynsane]

I used to run AAM with a 286 cam and ram pipe, works great

[Daveislandblue66]

This is pretty good for looking up SU needle profiles. You'll need to put AAK in as needle one, and then work through the others to find one that has the sort of profile you need.

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

I’ve just this second been looking at this.

I’ve put most of the Vizard recommended needles for this engine spec and I reckon AAA would do the job nicely assuming more elevated the line on the graph the richer the needle is?

Sort of, it is fuel flow rather than richness, but that's really the same thing. Don't forget a good 'old school' dyno operator will be able to file needles to modify the profile, so you just need to be close'ish anyway. And no two engines are the same, so 'the needle you need is' is nothing more than a starting point.

[Minigman]

Thanks for your help.

[Minigman]

Do you think the AAA looks a better bet than the current AAK ones?

[Daveislandblue66]

AAA looks to be similar to the AAK needle at the lower and upper end, but richer in the mid-range, so would probably be a good starting point.

Depends where you are taking it, but a good tuner will have a range of needles anyway, and once they've got as close as possible to ideal across the rev range, can do a bit of filing if there are any weak spots. When you book make sure that they are able to do what you want. I think there may be rolling recommendations in one of the other sections.

Though I'm not an expert in SU's, but restoring my current 45 DCOE Weber-equipped Mk1 back to nearer standard (removing the bulkhead airbox and putting the rotodip panel back in), and will probably switch to a pair of HS4's, and looking at needle profiles hence how I came across the mintylamb calculator.

[Minigman]

I’m giving Stephen Miles at Tipton Garage a go. He’s ex Janspeed and his dad was at Downton so have plenty of experience with the minis.

Previous to that I’ve used both Neil Slark and Dave Baskerville in Barnstaple with mixed results.

[timmy201]

So do you know if it's running rich or lean because you can measure it with a gauge, or just guessing?

I had a guy come around with a new Weber he'd just fitted. As he turns up he says - "as you can tell it's running really rich". We put on the AFR gauge and it showed idle and part throttle at 16:1 and higher - so super lean and bordering on engine damage. Without any kind of meaningful data it's really hard to get the needle right - in person or over the internet