Morris Minor Owners Club

Hi, can anyone tell me what sort of carb I have from these numbers?
exh 12g 1540 carb SU AUC 8092 Thanks!

does it have an integrated float bowl? What size is the throat?

It has a separate float bowl. Not sure on the throat size.

Well - that's not a carb part number - it's a 'heater suction chamber' whatever that is ! Check out www.sucarb.co.uk It would help if you can post up a picture - and stick a ruler across the manifold side of the carb and tell us the size of the hole !

Well, er, that's the trouble- I'm looking at it on eBay here in the States, and the seller doesn't know too much about it. I have a 1275 with dual carbs, and the seller says this came off a 1275. I guess I'm really wondering if this would be a better carb than the duals, as I'm more interested in economy than power.

If it came off an Austin America, it's a very clean install and nice setup. I believe it's a HS4. You will need the intake/exhaust manifold as well. The header pipes mates directly too. You'll need to ask him if it came off an AA. The only 1275 in the States were Spritgets and AA's.

Do dual carbs REALLY offer more power anyway?I'm not certain, and can't be bothered looking it up. but it strikes me that they're not gonna make all that much difference. I'm probably wrong though.

Hello Bazza,

there is no real reason that a twin carburettor set up is less economical than a single. In theory if it is more efficient then it will be more economical. basically it depends on it's set up and of, course, how you drive.

I know you think that your fuel is expensive now but using 1.84 dollars to the pound, our fuel currently costs about $8.00 a US gallon?

Alec

Bazza, Is this the carb? http://cgi.ebay.com/ebaymotors/AUSTIN-C ... dZViewItem
If it is, go for it. Bolts right up to a Minor with a 1275. You might have to change the needle if it was used on a smaller displacement Mini. Did the 1275 S have a single carb? I have one on my van with a 1275 and it works great. It also looks like it doesn't have many emmission related ports in the manifold. Without a air pump it's not a US spec if it's 1969.
It looks like a good deal.

The standard twin carbs provided by BMC etc are not much use - mainly because of the hopeless inlet manifold, and because each cylinder breathes in turn and so each cylinder 'sees' in effect a single small carburettor. There is little or no cross-flow. The power gains at the time were just because the twin carbs eliminated the hateful 'hot-spot' on the single carb manifolds. So - a big single on a GOOD inlet manifold (with NO heating) will out flow smaller twins and give more power. Also a whole lot less hassle to 'tune'. The part number quoted is for a cold start heater of some form (presumably fitted to the carb) - the carb indeed looks like a 1.5" HS4 - but to get more power with it you need a much better inlet manifold. The set-up shown there still has the hateful 'hot-spot' and will NOT give any worthwhile extra power. You need an alloy manifold with NO heating.

Thanks, everyone- yes, jaekl, that is indeed the carb. My duals work fine, but I keep hearing such praise for the HIF types that I thought a single was the way to go, and I guess I can't help fiddling. Since I don't intend to spend a bunch of money on an alloy inlet, I'll probably leave well enough alone. Thanks again!

Well - over here the good alloy inlets are about £5 ($10) on ebay. But yes - the HIF type carb is better in many ways, although power output is no more than the HS type.

Of course -you can improve your twin carbs by throwing away the standard inlet manifold - and fitting something more efficient!

bmcecosse, (without resorting to a trip to the UK), what do you suggest? Or, is there a way to improve the manifold I've got? Thanks

Trip to Uk (especially Ecosseland) always well advised!
You can bid on a single carb alloy manifold on UK ebay - and have it mailed to you. Being alloy - they don't weigh much! The one from an MG Metro is the one to go for - although there are various aftermarket versions about too.
The standard twin carb manifold - the modifications are detailed in Mr Vizard's excellent book on the A series engine (or Mini) - but years ago I made my own version with flanges to suit the head and slightly bent pipe about 4 ins long to flanges to suit the carbs. There is no need for a 'balance pipe' - straight stepless flow into the head ports is the aim. If doing all that work - I would (and did) make it for the larger 1.5" carbs - and fit two of them. That will definitely make an improvement!