Thanks for the note.
Jeff at Paltech uses the SM needle from a TR4 on his TR6 conversions, and Moss
sells their SU conversion with a BAD needle, which seems to be a bit leaner.
The Healey needle for an early 2912cc 6-cylinder is CV, which is not far from
the TR4 needle. Your ZH is the leanest of the bunch, just slightly leaner than
the BAD for stock TR6's from Moss.
Been awhile since I've posted.
About 15 years ago I converted to HS6 SU's. They came set up for TR6 by
Ted Schumacher with ZH needles (from Volvo 122S, I think) and red springs
and that's worked fine for me. My engine has stock cam, intake manifold
reworked a la Kastner's performance manual, ported and cc'd head, +.020
cylinders, tube header and free flow exhaust.
A few years later I helped a pal install an SU conversion sourced from Joe
Curto of NYC, who is one of the best on constant depression carbs. Don't
know what he might be using now, but on that setup he used the stock needles
for the HD SU on the Austin Healey 3000, Mk III. Can't remember what
springs were used. This TR6 was bone stock. They worked just fine.