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Hi, has anyone on here found a cure for carbs icing up ?. I've got a series 1 Land Rover with a 3.5 Rover V8 fitted with a 390 Holley carb. I've tried various air filters and ways of ducting warm air off the exhaust but it still does it. It will start fine from cold and tick over on fast idle with choke. After 1 or 2 miles it starts to miss-fire on low revs and will not tick over very well. If I switch the engine off and let the carb thaw out, it will run perfect afterwards. As stopping after 5 mins of every journey is not realy practical, I would like to hear of anyone's cures or suggestions to solve this problem.
Cheers, Rog.
Cheers, Rog.
Have you tried using an alchohol deicer fuel additive and keeping your fuel tank topped up to cut down on condensation?.....also if your fuel tank cap is really old it may not be sealing very well so a new cap may help.
My Isuzu came with a heated spacer block (between the carb and intake manifold) OEM, maybe you can find something to retro fit in?
>> Edited by Trooper2 on Saturday 24th December 02:59
My Isuzu came with a heated spacer block (between the carb and intake manifold) OEM, maybe you can find something to retro fit in?
>> Edited by Trooper2 on Saturday 24th December 02:59
I'm not a Rover expert by any means, but most all V-8 engines I have seen have a heat passage through the intake manifold, this diverts some exhaust flow from one cylinder bank into the other one - one exhaust manifold has a bimetallic controlled valve that closes it off most of the way when cold - the passage in the intake can plug in some cases.
If fixing what's there stock does not work, I would really think that ducting the intake from the filter down to a "stove" made of sheet metal on one manifold would likely work, and/or maybe you can find a carb spacer with an engine coolant heat feature. I would think a later model exhaust manifold would have these, or in any case it would not be that tough to fab.
In general, in my experience, V engines don't give problems icing the carb, but inline engines do. My MG-B '72 model, which of course has no carb heat of any sort, tends to ice the carbs at about the 5 mile point on any journey, like your rig if I shut it off for a minute the problem goes away. If I can get it through the "5-mile stagger" it finishes warming up and does OK.
If fixing what's there stock does not work, I would really think that ducting the intake from the filter down to a "stove" made of sheet metal on one manifold would likely work, and/or maybe you can find a carb spacer with an engine coolant heat feature. I would think a later model exhaust manifold would have these, or in any case it would not be that tough to fab.
In general, in my experience, V engines don't give problems icing the carb, but inline engines do. My MG-B '72 model, which of course has no carb heat of any sort, tends to ice the carbs at about the 5 mile point on any journey, like your rig if I shut it off for a minute the problem goes away. If I can get it through the "5-mile stagger" it finishes warming up and does OK.
Thanks for the info guys - it looks like I need some kind warm air intake. I have tried running 2 pipes from the exhaust manifold to the air filter but it didn't help things. Started it up yesterday after it had stood for 2 days and it ran for about a minute then the carb iced up completely. It would not run below 1500 rpm and was mis-firing like mad. Kept it running just long enough to get a bit of heat in the engine then switched off. Went back after 5 minutes and it had thawed out and ran perfect. It even does it when it is not realy cold - ie 5 or 6 degrees, especialy if it's damp weather.
If you have stock manifolds, on most factory V-8 engines I know of there will be a valve on one manifold that should be closed when it's cold, this directs some exhaust through a passage through the heads and in the middle of the intake manifold. You can see this passage usually and if you can see it feel it to see if it's warming up quickly after starting the engine.
I am about 99% sure your car has this, and 99% sure it's not working right. Either the valve is stuck open, or the passage is coked up. There are specific lubes available for the valve, if the passage is coked up I don't know any way short of taking the intake manifold off to clean it out.
Some "dry gas" added to the fuel might help, if the moisture is coming from the fuel. If this car does not get much use, there may be some water in the gas although I think your moisture is coming from the air.
I am about 99% sure your car has this, and 99% sure it's not working right. Either the valve is stuck open, or the passage is coked up. There are specific lubes available for the valve, if the passage is coked up I don't know any way short of taking the intake manifold off to clean it out.
Some "dry gas" added to the fuel might help, if the moisture is coming from the fuel. If this car does not get much use, there may be some water in the gas although I think your moisture is coming from the air.
Hi Mitch, thanks for the info. I have just been surfing the 'net for fuel additives for icing up carbs etc, and found lots of people with the exact same problems - on the motor bike forums !. They suggest using Silkolene Pro FST. It's a fuel additive that stops jets from icing up, carbs from sticking open due to ice build up etc. So I'm off to the local bike shops tomorrow to try to find some. I'll let you know what happens.
Just to update on the carb icing problem I was having - I bought some Silkoline Pro FST from my local bike shop and it has cured it. I put approx 200ml of it to £20 (23 litres) of fuel and the miss-fire, rough running and idling problems have cleared up. So I'm well happy now. Thanks again for your replies.
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