Burlen Fuel Systems is in England. Their web address is
http://www.burlen.co.uk/ They do respond to e-mail, and while I did use the
phone to order the catalogs, they do take credit cars via e-mail, even with you
breaking up the ca rd number into several different e-mails for quasi-security.
As for my bushings, I got lucky and had found them in a complete unused rebuild
kit at a flea market. Good thing I did, because I probably wouldn't have
actually ordered genuine correct SU bushings otherwise. I didn't understand
how sensitive this really is. Truthfully, good condition black bushings may
well work, I honestly do not know. I do know that lousy black bushings, with
non-SU bolts don't work worth a hoot!
You can certainly order the bushings and sundries from Burlen. Their prices
aren't bad, even including shipping and the exchange rate. I do not know if
the bushings and rebuild kits sold by the usual big players like Vicky Brit,
Moss and such are oem. Nor do I know if the kits sold by the smaller players
like SpitBits and are oem.
A nice thing about Burlen is they have everything, and not just marked as
"spitfire linkage" or such. They have parts diagrams and price listings for
all the individual bits that we sometimes need. So you can order a replacement
choke actuater arm, or a different bell crank, or just a replacement jet
without buying a whole rebuild kit.
You can also get all the different needles from them. Their parts catalog
doesn't actually list all the needles. Annoyingly, that's in a different
catalog that you have to buy (and I don't have the part number for it).
However, the Haynes Weber manual lists almost all the needles, with the
profiles. There's also a spreadsheet on the web that has them all, as well as
a selection program. This web page has the link to the SU needle selection
program, as well as nice instructions on needle selection and tuning.
http://www.team.net/www/morgan/tech/tuning.html I have an air fuel gauge for my
Spitfire to play tuning games with in the future. If the idea of having a
dashboard fuel mixture gauge tickles your fancy, this gauge is beautiful. I
don't have it myself, but it looks sharp
http://www.autospeed.com/A_0020/P_7/article.html . The link is old, so the
price is out of date. The company that makes it charges I think $60 for it.
As for inside tips for the single Stromberg, I don't have any special tips from
experience. But, I do not think that carburetor is inherently bad. In the
later models, it got all sorts of things attached to it that like to misbehave,
and make turning the thing right nearly impossible, especially if you remove
emissions equipment. But the basic design is perfectly good, and lives on many
high performance motorcycles. A whole lot of bikes use diaphram bellowed CV
carburetors.
Blanking off various components from the Stromberg eliminates their effect, and
their problems. You can get the carburetor back to the "undressed" mode fairly
readily, while retaining the visuals for emissions inspection. I'd also look
into finding an earlier intake manifold. I just learned yesterday that there
are large air passage and small air passage intake manifolds. My 1980 Spitfire
has small intake runners, so I'd guess that the early ones may have the large
intake runners. Since removing or blocking off the emissions controls
essentially eliminates some manifold leaks, you're going to need a needle
change (I think this is why so many of them run so rich). I'd try ordering
some of the early model needles as a comparison and reference. Again, Burlen
has lots of Stromberg needles, and the Weber manual has Stromberg needle
profiles. Although the listing wasn't as good, in that I have quite a few
Stromberg needles not listed in the Haynes manual. I'd also go ahead and order
the different piston springs from Burlen for experimentation, especially if the
rest of the engine was modified. I think the same spring was used throughout
the Spitfire time line with Strombergs, but I'm not sure.
All carburetors are sensitive to the air flow entering them, and virtually all
carburetors have poor entry shape from the auto manufacturer. Some sort of
velocity stack, even a very short one, will help fairly substantially. I have
no dyno numbers to give you for Strombergs to back this up, but the engineer in
me understands this. Edelbrock has made a small fortune selling a tiny
"velocity stack" for Holley carburetors that's only a half inch high, yet
produces enough improvement in basic air flow that it's detectable by seat of
the pants even. I see no reason that wouldn't be just as effective with a
Stromberg or SU, and would live inside the oem air filter box, being invisible.
With that, you should be able to make a Stromberg run well. Probably the
manifold change to bigger diameter ports would give the most bang for the buck,
especially higher up in the RPM range.
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