Single Carb from Twin Carb

[little_pete]

Hi, I've had my relatively newly bought morris at the garage for a week now for various niggles. One was rough running, the carb choke is sticking a bit so causing issues. I eventually want to mildly modify the carb, 12G940 head HIF38 carb and a nice in and outlet manifolds. So I'm on the look out for these parts (cheaply). I was going to buy an old carb and clean it up and fit a service kit. I've come across a carb which looks to have never been fitted, the problem is looking at the part number it is off a MGB 1972 and is the Front carb from a twin carb set up. Does anyone know if this can be used on it's own? oh also it's a HIF4 from what I can tell is just a slightly older HIF38. Any information would be greatly appreciated

[IslipMinor]

It should be OK, you will need to block off the fuel feed to the second carb (I think the feed goes via the front one?). Other than that check the dashpot spring is the one required for a Minor, and obviously check what needle is a good 'starter fo 10'.

Presumably it is either a 948 or 1098 engine? The crankcase vent connection on the HIF should either be connected to the front tappet cover (standard on the later 1098) or a 1275 timing cover. The rocker cover does not have the oil separator / flame trap and should not be used on a closed ventilation system, although people have used it. The risk is that it will suck oil straight into the carb!

[little_pete]

Thanks for the advice. It is a 1967 1098. At the moment it has a breather on the rocker cover going to the air filter. The tappet cover seems to have canister on it. I'll be getting a AAA needle by the sounds of it, I don't know about which spring is required.

[bmcecosse]

It will be fine....and try the spring that is within. AAA is what I use - seems ok but I know some use AAU.

[daveyl]

Out of interest has anyone tried the AAB needle in a 1.5 su? I only ask, as this seems to be a popular choice from 'minispares' shop. If you look on the 'mintylamb' comparorama website, the AAB needle is very rich.

I use an AEM needle for fuel consumption reasons. Gives me 5-6 better mpg and gives me tolerable acceleration.

[MarkyB]

The other thing to watch out for is that the cables will reach OK, sometimes there isn't much scope for change especially if the outers have been trimmed at some stage.

[little_pete]

Well I got the carb, a little on the pricey side, but when I factor in a carb rebuild kit on buying a second hand carb it makes sense.

Now to collect the other bits, I'm concerned about noise and the cost of a maniflow system how much benefit does it have over the standard system if I chop the exhaust manifold and use an alloy inlet manifold with it?

[bmcecosse]

If the engine is otherwise standard - then a standard exhaust will be fine for now. I changed mine - and noticed no significant difference.........except even more noise.

[JOWETTJAVELIN]

Out of interest has anyone tried the AAB needle in a 1.5 su? I only ask, as this seems to be a popular choice from 'minispares' shop. If you look on the 'mintylamb' comparorama website, the AAB needle is very rich.

I use an AEM needle for fuel consumption reasons. Gives me 5-6 better mpg and gives me tolerable acceleration.

I have used this needle on a non-Minor HS4 with good results.

[little_pete]

I'm planning on the 12G940 cylinder head otherwise standard. Got the carb, it doesn't seem to have a vacuum take off. Will I be able to take it from the manifold? (no brake booster)

[daveyl]

JOWETTJAVELIN said: I have used this needle on a non-Minor HS4 with good results.

Yes I am tempted to buy a AAB needle just to see what it goes like, as it's cheap. Did you fit it in a 'Mini'?

[JOWETTJAVELIN]

Nope. 1300 Allegro.

[IslipMinor]

Will I be able to take it from the manifold?

No, although the later MGB's with HIF carbs did, but the whole mechanical and vacuum advance set-up is very unusual and geared solely for emissions. Had forgotten that when you said that it was from a 'B'.

Can you take a picture looking at the carburettor from the engine side, so that we can see if there is anything that could be used for the distributor vacuum unit?

[bmcecosse]

There will be no harm taking it from the manifold. Not absolutely ideal - but it will be fine - it is how the vacuum is taken to the dizzy on many A series engines.