Warm air intake flap

[jbramwell]

As soon as my warm air intake switches to cold air the carby (solex 28/34) freezes. Do these things open too early when they get old? Also, the hot water circulation in the carburetor base, there is a 3/8" rubber hose coming out but how does the water get in?

[Chris_C]

What year is yours? I've been told the flap on both my cars is siezed, but it doesn't really affect me, I must look at it one day though to see how to fix it.

Only the early 1.7's had the water cooled carb bases, from memory they have 2 outlets. Later carbs have one hose outlet, which is fed to the crankcase breather, so could the hose be that and not the water cooling?

[jbramwell]

1990 and yeah it looks like it might be to the crankcase ventilation. I wonder if i could fit an earlier water heated type because this freezing is driving me mad.

[Chris_C]

The water heated type are awesome, but hard to find and a pain to plumb in. The later ones should have a ceramic preheater (as long as it hasnt' been replaced in it's life by the weber upgrade, which I don't like much at all, and went back to a solex). The ceramic preheater when working does as awesome job, it's on one of the two wires going to the carb, one being the idle solanoid, the other is the preheater. This are sometimes assembled wrong if taken apart, and then the thing shorts and blows fuses, so they just get disconnected.

Correct assembly is easy when you know how, but see if it's plugged in first!

[classicswede]

As I've never ran a 340 on petrol I dont know to much on this but I have loads of experiance on other carb engines.

Normaly on engies where the manifold is joined to the exhaust freezing is not a problem. The water heating is not normaly for heating when cold and then it actualy cools the manifold when the engine is upto temp.

On metro's with the sepetate inlet manifold its common to disconnect the water connections to improve power. This rather common 340 problem makes me think there are carb issues with 340's

[jbramwell]

Your dead right there. According to Wikipaedia the 340 is notorius for carburetor problems. I did replace the pre-heater thermistor and now it gets quite hot but only where the small thermister is housed. I have been reading a bit about warm air intakes and cold air intakes. warm air is compolsory in USA because cold air is denser and therefore the EFI creates a richer mix Conversely warm air is thinner so EFI gives a leaner mix. But with a carby, i guess the only down side of a warm air intake is a little less power. I can live with that if it prevents the freezing.

[jbramwell]

Ok, now I am really optimistic. Having had carburetor freezing problems for 2 years (since buying) I have replaced the floater, needle and seat, rebuilt the carby, shaved the base, replaced the thermister and now finally some joy. I have removed the thermostat from the air intake flap so that it does not open to cold outside air. Now, even when it is sleeting outside, the carby does not freeze when I blip the accelorator from idle. also , for some reason the idle is more even. Now for a nifty cable under the dash board so I can operate the flap manually in summer. Thanks to all for comments and moral support.

[classicswede]

Have you tried since the carb rebuild reomving teh hot air pipe?

Its wirth a try and all those carb issues could have been causing the freezing.

[jbramwell]

well I have done the opposite really, I have disabled the cold ait intake so now it only gets warm air and thus no freezing.