Heated manifold?

[Tim Dodd]

Hello everyone,
I have been looking at a traveller with a '1300' engine, a metro 13/4" HIF carb, and a water heated manifold. Now my question is what are the merits/demerits of the heated manifold? Are the travellers subject to icing? Isn't it better to have a cold air/petrol mix rather than a warm one? Doesn't it get hot enough under the minor bonnet anyway - I hear tales of fuel vaporisation quite frequently? Is it just a left-over from the metro that did suffer from carb icing, having the carb sat in front of the engine?
Tim

[Jefftav]

I think popular opinion is that it is not needed on the minor but opinions vary so it might be something you want to try and then see if it improves how your engine runs.

[RobMoore]

I have been looking into a similar set up fo my 1275.
On a combined inlet/exhaust manifold the inlet heats up due to being combined it also produces a hot spot.
Running seperate manifolde removes this hot spot but then the inlet does not get hot as before so some people often fit a water heated one. From what I can gather this is not really needed and only really reduces the amount and length of time the chooke is required.

[bmcecosse]

It will drop you some power - but it may help economy. That's why it's there! Twin carbs don't (generally) have heated manifolds - for v good reason!! It's no help with 'icing' - because it's after the carb - and icing occurs in the carb. The heat can't possibly flow back against the incoming cold mixture - in fact - there is an insulated block betwixt manifold and carb - precisely to prevent it heating the carb! Carb icing can only be prevented by providing a power robbing hot air stream into the carb - may be an essential in winter - certainly don't want it in summer.