engine size

Post by **Tris** » Wed Apr 05, 2006 10:19 pm

So when my scout leader told me "MG twin carb will fit that" it wont really make any difference?

Post by **chrisd87** » Wed Apr 05, 2006 10:31 pm

Twin carbs are also horribly difficult to keep properly in balance, and have all sorts of linkages between them waiting to go wrong. The twin carbs and manifold from an A-series midget will fit if you want to give them a try.

Post by **Tris** » Wed Apr 05, 2006 10:40 pm

Depends how much difference theyd make

Post by **rayofleamington** » Wed Apr 05, 2006 10:55 pm

I would have to spend £200 to get a burnt out unit and then start rebuilding it. any other options anybody

other options would be keeping an eye out on ebay and buying a runner for less than £100. It'll take a long while to find - certainly months not weeks. The other option is visit the MG messageboards - the MG1275 is fairly common if you mix in the right circles

Post by **chrisd87** » Wed Apr 05, 2006 11:05 pm

I think the main problem is that he's in Northern Ireland, with most 1275s being over here...

Post by **Cam** » Thu Apr 06, 2006 1:14 am

Tris wrote:So when my scout leader told me "MG twin carb will fit that" it wont really make any difference?

It will fit, but it might well make it run WORSE! Properly set-up it will be better than a standard 1098 carb but so will a HS4 (Mini 1000 carb).

The thing is that years ago a period modification was 'twin carbs' and it's kinda stuck in people's minds. For example a mate of mine had a new Fiat Punto and it was a 'sports' model. His dad asked him if it had got twin-carbs.

Now that's an absolutely mad question to be asking nowadays, but the concept of twin-carbs = sports performance seems to be stuck in the minds of folks who were around when that was a valid assumption.

Post by **Alec** » Thu Apr 06, 2006 6:26 am

Hello Cam,

I think you missed the point I was trying to make, I was not arguing Weber versus S.U. but that a twin half Weber set up must have given an advantage over a single full Weber which is down to manifold performance. By the same reasoning, I don't see how a single would give better performance over twins (Given equal total flow capacity).
Simpler and cheaper but having said that twins do not require constant tuning or are even difficult to tune. I would happily use either set up dependant purely on availability or price.

Alec

Post by **Cam** » Thu Apr 06, 2006 2:45 pm

Hi Alec,

A twin-weber setup should only give an advantage if the single is too small and therefore the 'twin' set-up will flow more air/fuel than the single. If the single is large enough and the manifold/filter are optimal then there should be really no advantage or disadvantage to either setup with the exception that the single will stay 'in-tune' for longer and be a lot simpler to set up.

According to Mr Vizard and his tests, the actual characteristics through the rev range are slightly (but only slightly) different (single vs. twins) and there might be a slight power increase at top RPM with the twins but less lower down (could be due to a number of things including manifold design). The total 'area under the curve' is about the same though, so if you are not at top RPM constantly (i.e. not racing) then you'd be better off with a single. But we are talking very small amounts of power here. More than likely not noticable on the road anyway.

The twins DO take more steeing up as you have to do the mixture twice and set the butterfly linkage to even out the air flow to the two carbs. It IS much simpler to do a single carb and that single carb does not have to be matched to another so it's easier.

I agree that a new twin-carb setup can be set and it won't go out of tune that quickly, but a single NEVER will (air wise) and also most people nowadays will be buying worn 2nd hand units with play in the linkages and worn parts which WILL go out of tune and are awkward to set up for the inexperienced amateur.

Post by **Alec** » Thu Apr 06, 2006 4:11 pm

Hello Cam,

I was talking racing units, and seeing how long the 'better' double DCOE manifolds became to give good flow and distribution was quite interesting, virtually joining the driver in the cab (Minis by the way)
The twin 'half' DCOE was a lot more compact and direct.

Alec

Post by **Cam** » Thu Apr 06, 2006 5:36 pm

Yes, I noticed that too! In fact one modification for the Weber carbs was to chop the bulkhead and weld in a mini battery box to give more space. Hmmm. A battery box in the middle of the bulkhead! Sound familiar?

Post by **paul.kissick** » Thu Apr 06, 2006 9:39 pm

Okay then twin against singles. Single big ones win. if i was going for the look of the car would u think a twin set of su's would be better lookin than a single? would the sound of the car change with twins on it?

Post by **Cam** » Fri Apr 07, 2006 12:18 am

Yep, twins look better and will do more or less the same job really. It's up to the individual to decide what they want on their car.

Not too sure about the sound. I'd say they would sound the same.

Post by **bmcecosse** » Fri Apr 07, 2006 2:20 pm

Need to tell the insurance co about twins. A single is a single - just a replacement from the scrap-yard!!

Post by **Peetee** » Fri Apr 07, 2006 3:52 pm

A single is a single - just a replacement from the scrap-yard!!

"But I got it from a 1000cc mini. I thought it would be the same size, honest"