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GT6 SU carburettor needles


Doctor slow

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I have HS6 carburettors replacing the strombergs on my Mk 3 GT6. It has a fast road camshaft, (but I have no information on which one), and a 123 distributor. The needles in the carbs are BAE, and I'm not convinced that these are ideal. Looking on the SU charts, obviously triumph gt6 is not listed, but TR6 is listed as a conversion from strombergs, and the needles recommended are BAG's. Looking on the "mintylamb" website, and comparing the two needles, it would seem that the BAG's are leaner at low revs, and richer at high revs, which may be better. The only reference to BAE needles that I could see on a quick skim through the data  was for Rolls Royces! Anyone have any experience of the SU conversion on a  GT6 and needle selection. 

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If its a 2.5Litre -

The Stromberg TR6 has a low compression head and a very un-sporting camshaft. So avoid any comparison. Also avoid the 2500s saloon needles, BDB, as they are to weak. 

Use BAE or BDQ which are weaker. Use either yellow or green carb springs.

If its a 2 litre use the standard Mk2 Strombergs with heavier springs.

Dave

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If you are using the HS6's on a 2 litre car, my ancient TriumphTune manual BAE needles for a car with a flowed head and a fast road cam. 

But the reality is that everybody is just guessing and trying to get a match. What you need to do is book into a rolling road who understand SU's, and get them to either change needles, or more likely, reprofile the ones you have. They can also set up the distributor curved for you.

Money well spent, the car will drive better and be more economical after.

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Well, yes, I haven't been able to find a rolling roader - obviously not looking hard enough, or in the right places. My friend with and Elan also hadn't been able to find one (or at least, one that knows what a caburettor is!) Anyway, thanks very much for that, I'll give him a ring........ but may not be getting it done until we're out of house arrest - only managed to even drive it about 100 miles since I got it just before Christmas.

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If you fancy some trial-and-error tuning check out https://tecb.eu/onewebmedia/Tuning_SU_Carbs.pdf

Tells you all about SU carbs/the different 'steps' in a SU needle profile and a testing procedure (P11).  Basically tuning for idle then testing across the RPM/load range both with and without some choke.

A rolling road (with a good operator who understands SU carbs) will would be better, but also more expensive and possibly less fun if you enjoy tinkering on your own.

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