Greetings, Earthpeople, Triumphisti, Sidescreeners. I have a few SU
needle questions, if you please. But first, a sharing of
experiences. Yesterday Sharon and I drove the GT6 to the White
Mountains (NH) for a day of climbing Franconia Ridge. The weather
and the mountains were spectacular. The car ran well, nicely smooth
with newly rebuilt driveshaft, new old Cosmic wheels, and new tires.
One of the more entertaining things about such a trip is the number
of people who twist their necks and stare, probably wondering "What
is that?" One old codger in the passenger side of a pickup towing a
battered racecar gave a nice wave. At a gas stop on the way home a
guy walked up and asked "Um, a GT3?" "No, a GT6." "How are the
Lucas electrics?" Turns out he just finished 8 years of rebuilding a
'73 E-type roadster.
Now the needles questions. Many years ago a DPO fitted this car with
K&N air filters and a pair of H4S's from an '80 MGB. He did not
attempt to re-calibrate the needles or springs. Some time ago I
replaced the springs with stiffer "yellow" ones as specified for the
TR2000 engine. That helped a lot. However the accompanying needles
were way too big, too lean, so I'm still running the MGB needles,
still chasing a good mixture. If I set it right for idle or even a
few flats richer, it is too lean for cruising but seemingly okay at
full throttle. With a warm engine so the dashpot oil has thinned
out, it occasionally stumbles when I open the throttle a little. So
yesterday I pulled the choke a little, and as expected, the stumbling
stopped. More importantly, the engine smoothed out while running at
steady throttle. Without choke it would burble, sort of like
brrrbababrrrrrrrrbabrrrrrrrbababrrrrrrbababrrrrr"; with a richer
mixture it settled down to a clean "brrrrrrrrrrrrrr". Okay, so it
wants to be richer even at cruising. I could simply crank the jets
down a lot, but I also want it to be cleaner at idle. Of course,
poor burning is dirty no matter how it is set. The curious this is
that at 2500rpm it seems fine though the engine doesn't pull very
well below 2500rpm, at 3500rpm it definitely isn't, at full throttle
it seeems fine.
I've run the haystack SU needles program to search for options.
Before the results mean anything to me I need to know how big a
thickness change has to be to be significant, and how one knows what
part of the need one is running at. At idle one is obviously running
at station 1 (or 2? if the jets have been screwed down a lot). What
part of the needle is typical of highway cruising at 3500rpm? I'm
going to contact Joe Curto on this but I'd like to have more info
first and I don't want to waste money on useless needle fiddling.
Tanks,
Jim Muller
muller@pop.rcn.com
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