7 replies to this topic

[GeraldTheMini]

Would anyone be able to advise me a starting point on what needle to use, just to get me ran in and moving? I do plan on having a proper tune/custom needle/rolling road in the future.

Spec is newly built as follows,
998 A+ +20, flat tops
Modified head (big valve stage 3, if you like)
SW5 camshaft
Exhaust and inlet manifold
K&n filter in std housing

[stuart bowes]

could start here: https://www.classicm...chnical/needles  and here: https://tecb.eu/onew...ng_SU_Carbs.pdf

 

just some interesting notes until someone gives you more specific info for your particular build

Edited by stuart bowes, 13 November 2025 - 12:56 PM.

[GeraldTheMini]

Currently got a ABD for reference.

[GeraldTheMini]

Just to add now I've done some research and progressed a little. Engine ran in fine on the ABD. Lambda was very close to 1.00 from idle up to around 2750-3000rpm. I've now done some roadmiles on the new engine, it leans out 3000rpm+ rapidly. (1.25 lambda). Would I now be sensible to try something like an AAF. Very near profile to the ABD but decreases in diameter lower down the needle.

[GeraldTheMini]

Photo of the plugs after 10 mile journey mixed driving.

Attached Files

•  PXL_20251227_155317924.jpg   67.38K   4 downloads

Edited by GeraldTheMini, 27 December 2025 - 04:17 PM.

[imack]

AC Dodds new AFA profile might be worth looking at.
Designed to stand a chance of being in the ballpark for 998's with stage 1 kit.

Edited by imack, 27 December 2025 - 04:58 PM.

[PoolGuy]

Just to add now I've done some research and progressed a little. Engine ran in fine on the ABD. Lambda was very close to 1.00 from idle up to around 2750-3000rpm. I've now done some roadmiles on the new engine, it leans out 3000rpm+ rapidly. (1.25 lambda). Would I now be sensible to try something like an AAF. Very near profile to the ABD but decreases in diameter lower down the needle.

Why not thin down the needle that you have, it's not rocket science. All you need is a drill and some fine emery paper. It's easy to work out where the needle is sitting at the 3k rpm mark. As you have an AFR it's a simple process, just take it easy while you're starting.

[GeraldTheMini]

Update - fitted AC Dodds new AFA needle. Once baselined it runs perfectly without any modification needed. Very nice and consistent lambda reading right through the rev range (stationary) Will post again once I've got some miles in at different engine loads.