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.
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
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?
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..
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....
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.
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.
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.
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
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.
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
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!
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.
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
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 .