SU 1 1/4 inch Carburetors

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Model T Ford Forum: Forum 2013: SU 1 1/4 inch Carburetors
Top of pagePrevious messageNext messageBottom of page Link to this message  By Jeremy Gibson on Wednesday, May 08, 2013 - 05:07 am:

I'm building another speedster at the moment and I have fitted twin 1" 1/4 SU Carburetors. But I'm having trouble setting them up.

Has anyone done this before and if so could you point me in the right direction needle wise please?

I'm running on D5 at the moment, as they were when they came off an MG midget.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Roger Karlsson, southern Sweden on Wednesday, May 08, 2013 - 05:35 am:

Someone has done that, I think I've seen pictures of a nice UK speedster with SU carbs in a book, was it the 1987 "Super profile" book by Michael Allen? http://www.amazon.co.uk/Ford-Model-T-Super-Profile/dp/0854295879/ref=sr_1_28?s=b ooks&ie=UTF8&qid=1368005165&sr=1-28&keywords=model+t+ford
But it's rare in the US or other countries.. perhaps you can find that SU equipped speedster builder in the UK T club?

I'd be interested to hear about your results, older SU carbs with brass details looks period enough for me, might try it myself :-)


Top of pagePrevious messageNext messageBottom of page Link to this message  By Roger Karlsson, southern Sweden on Wednesday, May 08, 2013 - 06:15 am:

I just read about the colortune way to adjust carbs - it's a spark plug with a glass insulator so you can see the color of the combustion. May need two plugs for adjusting double carbs, though. http://www.ebay.co.uk/itm/Gunson-Colortune-tuning-tool-for-classic-cars-/1706748 18644?pt=UK_Diagnostic_Tools_Equipment&hash=item27bd030e54

Plus adaptors from standard 14mm thread to Ford's 1/2" pipe thread, available from the vendors: http://www.modeltford.com/item/14MM-AD.aspx

Anybody tried colortune for adjusting carb settings?


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ricks - Surf City on Wednesday, May 08, 2013 - 07:40 am:

I have a colortune, and used it once or twice. It's fine for setting the idle, but a bit awkward to adjust for power at 30mph...

I remember something in Rodent Track or one of those rags describing English sports cars, and one of the comments was the SU carbs always out of tune..


Top of pagePrevious messageNext messageBottom of page Link to this message  By Chris Barker, Somerset, England on Wednesday, May 08, 2013 - 10:36 am:

SU carbs are fine - used on millions of Minis, Minors, Austin Healeys, MG TC, TD, TF, MGAs, MGBs, Midgets, Sprites, Jaguars etc.
Simple to set up and adjust.
Just Google 'tuning SU carbs' and go from there....


Top of pagePrevious messageNext messageBottom of page Link to this message  By Mark Gregush Portland Oregon on Wednesday, May 08, 2013 - 11:14 am:

I forgot about the colortune it's been a while since I worked on my Minor or MG. The other tool is a device you put over the intake of the carb so you can balance each ones air intake at idle. When 2 SU's are used, there should be a balance tube between the two intakes.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ricks - Surf City on Wednesday, May 08, 2013 - 12:11 pm:

Uni-syn, Mack. I have one of those, too. I let the first one go with my TD, back when it broke the crankshaft. I bought the second one when I needed to check air flow through some airline avionics boxes in the 1980s.



Avionics bay below the cockpit in a DC-10.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ricks - Surf City on Wednesday, May 08, 2013 - 12:15 pm:

I looked long and hard at used Jaguar sedans, beginning in the 1980s.

Those with 1978 and later advised buying 1977 or older with SU carbs.
Those with 1977 and earlier advised buying 1978 or later with EFI.

We finally bought a '93 in '99, and it was a great car. There was still just enough Lucas in it to keep it technically interesting.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Bud Holzschuh - Panama City, FL on Wednesday, May 08, 2013 - 12:18 pm:

Jeremy

Many moons ago when I was heavy into Brit cars (and money was in short supply), we used to balance the carbs using a 2 ft length of rubber hose.

Hold one end to your ear and the other near the intake of each carb, if they arn't balanced you will hear it easily. Unless they're balanced, it will never run right.

High speed mixture adjustments were done by raising or lowering the needle with the "c" clip and inspecting the plugs after a run.

All from memory .... as I haven't fooled with SU's in 30 years.

Cheers


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ricks - Surf City on Wednesday, May 08, 2013 - 12:19 pm:

I looked long and hard at used Jaguar sedans, beginning in the 1980s.

Those with 1978 and later advised buying 1977 or older with SU carbs.
Those with 1977 and earlier advised buying 1978 or later with EFI.

We finally bought a '93 in '99, and it was a great car. There was still just enough Lucas in it to keep it technically interesting.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Fred Dimock, Newfields NH, USA on Wednesday, May 08, 2013 - 12:29 pm:

My "How to repair your foreign car" manual says that carburetor is a French word meaning leave it alone
But if you insist on not doing as you are told you might visit these sites: :-)

http://www.zhome.com/ZCMnL/tech/su.html

http://www.moreg.org.au/carburettors.htm

http://sucarb.co.uk/technical-hs-type-carburetter-tuning-single


Top of pagePrevious messageNext messageBottom of page Link to this message  By Jeremy Gibson on Thursday, May 23, 2013 - 10:06 am:

Just thought I would update you all.

I have now moved to twin 1"1/2 SU Carburetors with AAA needles, and things are looking up. I don't think i'm far off being correct. Happy days!


Top of pagePrevious messageNext messageBottom of page Link to this message  By Jim Rutherford on Thursday, May 23, 2013 - 10:45 am:

Jeremy,

I saw that you are in the UK so that may explain to some why you are using SU's. Clever idea to my way of thinking. Any comparable vehicles that may have used SU's similar to yours? I'm thinking MG Magna, or maybe a bigger pre-war Austin or Morris? I'm guessing...

Best of luck. I would love to see a pic of the setup. Assuming you fabbed an inlet manifold?

In my book, the Colortune is worthless but the Unisyn is helpful. The piece of hose to my ear worked best for me.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Terry Horlick in Penn Valley, CA on Thursday, May 23, 2013 - 11:16 am:

There are some good SU manuals which will walk you through the procedure of profiling your own needles. I like the one I have: "How to build and power tune SU carburettors" by Des Hammill on Speedpro Series of Veloce press. If you buy the little tool set for the SU carburetors it has a nice little instruction sheet which explains the setting procedure.

I don't know which needle you need. Are you running twin SU's or a single? I've seen singles on speedsters here in Califunny, USA, but not doubles.

I run a stock set of 1 1/4" SU's on my TC. I end up having to clean them out and readjust them every ten years. I second the Uni-syn first, the color-tune, but then finish up with a Gunnison Gas tester. Then road test it to decide if you like the profile on the needle. I also fiddle with the oil viscosity in the dampers.

I have a big-ass set of SU style carbs off a Datsun 240Z which would run a speedster just fine (probably only need one) if anyone wants them.

TH


Top of pagePrevious messageNext messageBottom of page Link to this message  By Victor Bloxsome on Friday, May 24, 2013 - 05:08 am:

I have seven SU carbs and five SU electric pumps between three cars - 1936 Alvis Speed 20 , MG SA saloon 1938 , and MG A 1957 sports .

Victor in Australia .


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