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erohslc
erohslc Dork
10/6/15 8:41 p.m.
wspohn wrote: "Burlen is reintroducing the dual choke SU carb, the DU. Prototypes were shown at the Goodwood Festival. Sizes will be 1-1/2 and 1-3/4" That link doesn't work - do you have an URL for this? Very interesting. I know some guys that would run these instead of Webers, just to be different!

That was the URL. I just clicked on it from the posting and it worked, but maybe because the URL was still in my cache.
Here, with quotes:

"https://us-mg6.mail.yahoo.com/neo/b/message?search=1&s=Nz5wn_BkhTz8BSneov4-&encryptQ=1&startMid=0&sort=date&order=down&mid=1_0_AFfuw0MAAAK7Vf%2FHfwDPCPIxtu8&fid=Inbox"

The bottom of the linked page says: Simply send an email to DU6@sucarb.co.uk expressing your interest and you will receive regular updates specifically about the new Carburetters.

Basil Exposition
Basil Exposition Dork
10/6/15 11:09 p.m.

Looks like the URL to something in your Yahoo email account or something you accessed through it. It isn't working for us. Maybe if you post your Yahoo username and password we can view it. JK

erohslc
erohslc Dork
10/7/15 6:59 p.m.

Yeah, I'm on their email list and that arrived.
I searched for, but didn't find a Burlen DU link.
Meanwhile, something like this for a Spitfire ...
(vaguely sexual I think)

http://forums.ctzcc.com/files/su_du_6_dual_throats_1959_60_123.jpg

NOHOME
NOHOME UberDork
10/16/15 3:22 p.m.

Just finished a E36 M3 show where I installed a professionally rebuilt set of H type carbs on a guys car. They were beautiful to look at and the car ran fine. Of course they pissed fuel out the bottom of the jet assembly. Cause there will ALWAYS be some issue with an SU carb!

Absolutely brilliant design, but they can't quite execute in the real world. There is a reason that the DGV swap has been so successful.

erohslc
erohslc Dork
10/16/15 4:43 p.m.
NOHOME wrote: Just finished a E36 M3 show where I installed a professionally rebuilt set of H type carbs on a guys car. They were beautiful to look at and the car ran fine. Of course they pissed fuel out the bottom of the jet assembly. Cause there will ALWAYS be some issue with an SU carb! Absolutely brilliant design, but they can't quite execute in the real world. There is a reason that the DGV swap has been so successful.

Gee, I've only been doing SU on LBC for 45 years and NEVER seen an SU that '... pissed fuel out the bottom of the jet assembly...' except when someone screwed the pooch on the build.
Given that a properly adjusted float will maintain the fuel level below the jet opening (assuming someone RTFM and didn't fit a high pressure fuel pump),
and that the fuel tubes are crimped to the jet, the only way they would leak is if someone has seriously damaged something or didn't bother to properly connect the fuel line to the float bowl chamber.
As for DGV swap, hahahahaha, lists are full of unsuspecting newbies that heard 'Weber', got stars in their eyes, and thought they were bolting on some serious kit.
Then #1/#4 runs lean while #2/#3 runs rich, or vice versa, the crankcase pressurizes and blows oil out the dipstick tube, vac advance port doesn't function the same for the dizzy, they spend a bunch of extra time and money buying and trying various jets and tubes trying to get the damned thing to run properly ...
Is that the DGV 'success' you are referring to?

Rupert
Rupert Dork
11/2/15 12:15 p.m.

In reply to Basil Exposition: You don't use Webers? Wow are you missing out on a lot of good fun. Carrying a whole box of jets out and finding you never have exactly the right ones for that moment in time, tuning for cool and damp conditions then retuning for hot and dry between heat races, having everyone else in the pits who uses Webers bothering you for spares, or bothering everyone else in the pits using Webers for spares because none in your box of parts works on that specific day, at that specific time of day.

Man why would anyone use SUs or Hitachis? They're not nearly as easy to blame for your terrible laps as Webers are! And you might actually have time to study the course, eat lunch, and plan for your next time on the track. How boring!

But then that's my opinion & I've trod both trails. Others might not agree. And looking at their results, they're right in their case. For me at least the switch/s to Webers hasn't ever been the end-all be-all I expected.

frenchyd
frenchyd Reader
11/3/15 6:09 p.m.

In reply to Basil Exposition: It's pretty standard that if you have a properly set up set of Webers they will make 15 horsepower more than the 2 inch SU's on a Jaguar. Of course With Webers you needs to have a properly calibrated air density meter that you treat like the crown jewels.. That and a really complete set of jets (60 isn't nearly enough) along with pages, (and pages, and pages) of dyno sheets with tests at various air density figures.

Rupert
Rupert Dork
11/4/15 11:58 a.m.

In reply to frenchyd: Yes I had three Webers on mine. Both times, maybe it was three, that I got them perfect it was a perfect ride. However most days I spent more time watching the clouds than watching the track change.

VClassics
VClassics Reader
11/4/15 4:24 p.m.

My take is that carbs cannot make power, but they can restrict it. If I build a 140 HP Volvo engine, a pair of 1.75" SUs will support that just fine, and there's no advantage in going to 45DCOEs (which I'd have to choke down pretty far in any case). If I build a 180 HP engine, SUs won't flow well enough to support that, but DCOEs will.

It takes some effort to get the Webers jetted right -- a dyno session is very helpful -- but I've never found that they were at all picky after that. I ran a pair of 48DCOs on a daily driver for years, rain or shine, hot or freezing, and never felt any need to change jets.

Rupert
Rupert Dork
11/4/15 7:01 p.m.

In reply to VClassics:

WOW!! I've never heard anyone say that before! After I got my 3 on my Jag and my 3 on my 240Z jetted right they ran great once or twice. The rest of the time they ran OK. Unless of course I spent more time jetting than driving. But when the next weather front came in, they were back to OK. How many jets do you have for your Webers? I often found 100 weren't enough for three carbs at a time.

VClassics
VClassics Reader
11/4/15 7:27 p.m.

I've never had a triple setup, which of course would make syncing them that much harder and require half-again as many jets. I really haven't found that they are at all sensitive to temperature or humidity, and they will automatically compensate for air pressure to some extent.

The engine I use for my avatar went into a Carrera Panamerica race car which won the 2-liter class in 2009. That year's running went from sea level in the south of Mexico to over 9000 feet elevation with patches of snow on the ground, and they did just fine with just a selection of three main jets (they did have a wide-band AFR gauge in the cockpit). I'm sure that wasn't optimum at altitude, but they did just fine with it.

On the Volvo engines I deal with, I know that F2 tubes will work with big cams and F15 will work with mild ones. Low-speed jets are either going to be 55F8 or 60F8. Air correctors are going to end up 40 to 50 points higher than the main jets. I've never had to mess with the pump jets or drain. Chokes with depend on the cam and displacement, and those are predictable. That just doesn't leave all that much to experiment with.

Rupert
Rupert Dork
11/5/15 3:23 p.m.

My hat's off to you!!

maseratiguy
maseratiguy Reader
11/5/15 8:57 p.m.

I've had SU's on my Volvo's and Webers on my Maserati, (3 2barrels). Both are great and once adjusted the Webers run fine for several years w/o issue, (but no, I don't drive it in the Winter months). The SU's also run fine with a seasonal tune, (then again I am doing valves etc.) I must note though these are on stock motors and set up as stock as they are meant to be.

wspohn
wspohn HalfDork
11/9/15 9:34 a.m.

I have a bunch of Webers in operation but I have a definite soft spot for SUs too.

This is a triple carb system I created for an MGC.

dougie
dougie Reader
11/9/15 11:21 p.m.

I run triple SU HD8's on my '57 100-6 MM Austin Healey vintage racer. I chassis dyno every spring before the race season to fine tune everything, after that I don't touch the carbs for the rest of the year. My SU's have been very reliable for the past 10 years on tracks across the US at different elevations with little to not adjustments.

<img src="DSC09702" />

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