I want to change my updraught carb to a SU ,I have been told an early (1930,s) Morris Minor carb will bolt straight onto a post 30 manifold,as these are as rare as hens teeth ,what other carb will fit even if I have to make up an adaptor plate ? I presume I will need a carb with a 1" bore.

Nigel

I converted my later ruby type engine to an SU. I originally was going to use the Morris Minor 1 inch carb as you say, BUT they aren't all that common and a bit pricey. I eventually used a later Morris Minor inch and a quarter SU and made an adaptor plate for my later Ruby style sidedraught manifold. The plate altered the "phase" of the bolt holes by 90 degrees to allow fitment, and I filed the locating lug on the float chamber to allow it to sit level.
My conversion suffered troubles over a number of months which were eventually traced to a cracked manifold! When it was running right it really made a big difference, the car was not faster in top speed terms, but it would really pull well up hills.

You may be aware of a number of different manifolds and adaptors which are available for such conversions from the usual suppliers and sometimes ebay. If I get around to refitting the SU I will most likely look at using one of these proprietery castings , as the conversion plate to alter the phase and taper the bore etc is not as straightforward as it seems and could comprimise reliabilty because in opening out the bore or "eye" of the sidedraught manifold things get a bit thin and marginal in the gasket department!

Not really much of an answer I know but gives you some more to think about!

Steve

Hi Nigel I put a 1" on my 1931 Austin 7 before driving back from Beijing this year. I will never never return to the updraft Zenith, the car really shifts, I got at a peak 52 mpg never less than 40 the other car on the trip had an updraft for every 5 gallons he used I used 4 gallons his jets got blocked time after time, me never, get one I run on an EB needle as that was fitted and is a weak MG M type 1930.

Fit and forget!!!

Chris

Thanks for the replys, I looked at Vince,s car and see he fitted one also.

Interested to read the comments about the SU conversion, as I have been thinking along those lines myself.

However, and this is an interesting possibility, in the latest edition of Practical Classics (to be concluded in the next issue)there is an article on retro-fit of an electronic management fuel injection conversion - suitable for 4-cylinder engines - now that got me thinking!

Ditch the carburettor & dizzy in one go!

I am interested to read the results of the ocnversion on terms of fuel economy & power output - these will certainly improve - next issue of PC is eagerly awaited!

So, there could be other possibilites other than SU!!!

Would really propel these old cars into the 21st Century!

Gary

I have a spare programmable ECU and associated hardware from my hooligan Escort days, which I suspect with some clever thinking could conceivably run my Austin.

I wouldnt do this though for many reasons....

The fuel pump and ECU draw more current than the dynamo supplies!!

It would spoil my enjoyment of the "mechanical" Austin Seven.

A well set up SU carb is a very very good bit of kit, but the ignition timing control/spark etc is the real issue that will be affecting driveability in our case.

In light of this I suppose that an electronic trigger instead of the points would improve matters, but I guarantee most of the readers of this forum would not be impressed!!!

Some contributors have fitted modern distributors with different advance curves and less wear in them, which seems to be fairly acceptable and works well.

As for the full ECU set up......

Its something I have thought of and then discounted as a step too far, just enjoy fiddling with your dizzy and carb!!

Steve.

Would I be right in thinking an early SU HS1 1 1/8" is the only su really suitable, or would a later hs2 1 1/4" be ok

Every now & then on this site there appears conjectures on what modern, mostly electronic, gizmos can be applied to Austin Sevens, all of which makes me wonder why the writers own one. Apart from improvment with perhaps brakes and 12 volt systems for safety reasons, there's nothing wrong with a properly-restored Seven. It will do the tasks it was built to do, be happy with what it is. I'm mindful of a Longleat Rally 30 years ago when, after being shown all manner of 'clever mods' by the proud owners, Stanley Edge said to me "I wish they'd leave the bloody things alone". Now someone's going to ask who he was. Correspondence welcome - I have a very large WPB. Cheers, Bill in Oz

.


Bill,

You are very privileged to have had conversation with the splendid gentleman.

Oh, and by the way, I agree with your sentiments, and his.


Mike

I ran my unblown ulster on a 1 1/8" and a 1 1/4" and both were fine. If you have the bigger carb then you might not get the piston fully lifting but that's not much of a problem. It really depends on valve sizes etc. With a standard engine I'd stick to 1" or 1 1/8".

And personally I prefer the H series to the HS simply because the plastic jet plumbing is ugly!

Charles

Mike, you're so right about Mr. Edge. Lest anyone thinks I was a close friend, not so. I only conversed with him personally twice by which time he gave me permission to copy his A7 design notebooks (then in the custody of Ian Dunford), later I visited him at home. Out of 20 million people in Australia at the time, I was lucky (at Stanley's request) to locate and re-unite an old friend of his who had migrated and with whom Stanley had lost contact. After that it was Christmas cards and his very interesting replies to my many queries about Sevens via correspondence. For someone who'd been away from it all for so long his memory was outstanding. I'm sure like me he wouldn't object to up-to-date replacements of "innards" such as c/shafts, rods, pistons, cw&ps etc as that was being done by anyone whilst the car was in production. My grumpy old message was directed more to those who obviously aren't happy with their Seven & to remind them that this is an AUSTIN SEVEN website and not a venue for those stiving to spoil it's charm with modernisation - there are other sites for electronic gadgets & wizadry. Finally I was indeed priveleged to attend, with many other Austin Seven enthusiasts, the graveside Service for Stanley in '92. Not only was Stanley Edge a brilliant man but a true Gentleman. Cheers, Bill in Oz

I would have to agree with Bills sentiments most of the time.
The whole point of owning a Seven is to enjoy the experience of motoring in that era.

There are a couple of exeptions...

Specials..... These are outside classification really because they can be so many different things and of course they were built in the period as modified or home brewed vehicles!

And of course most people would rather see a car on the road being used and smell the oil , see the smoke, hear the engine etc etc even if it has some bits changed here and there to keep it going or make it safer on the public road, rather than see some totally original car still with its original air in the tyres stuck forever in some awfull prison they call a museum!

Enjoy your car for what it is, and use it.
If its original then try and keep it that way, if its not , then so what just use it and enjoy it anyway!

Steve