carb condensates really bad

[LAC_STS]

Didn't want to steal FillupD's thread about his air cleaner condensation but I have been wondering about the same thing but on my carb which is an Edelbrock 1409.

It always condensates really bad on the outside of the carb. But I noticed when I was looking down the throat of the carb while underway or when I get back to the dock after running that there is condensation on the primary throttle plates. My flame arrestor does not ever condensate. Not the old all metal type kind nor the K&N one I just installed recently when my metal one fell to pieces.

I wonder if this is normal for one and also how can it be safe/normal/ok for water to condensate and get inside the carb throats?


So, is this normal or is this a problem and I need to fix it? If it's a problem how would I fix this or minimize it?


When I was siting on my boat at the dock at the marina where I keep it the forklift guy that works when the regular guy is off came by, he is a mechanic there. I asked him about it and he told me that all Edelbrocks do it.


Much thanks

 

[Aloysius]

Re: carb condensates really bad

On one hand, it means you're getting nice cold air to the carb. Perhaps a little too cold, especially with ethanol tainted fuel. aircraft use carb heat to prevent this, as did carbureted cars.

Slightly warmer intake air would prevent this, yet not cause a loss of power.

What you see may be ethanol condensing out. Try non-ethanol fuel and see if the phenomenon reoccurs.

 

[Alpheus]

Re: carb condensates really bad

Not just edelbrocks, all carbs do it. Its from the venturi in the throat of the carb. Doesn't matter what type of fuel you use.

You should see an airplane carb (Lycoming), it forms ice on it at quarter power on 90 deg days.

One disadvantage of the float-type carburetor is its
icing tendency. Carburetor ice occurs due to the effect
of fuel vaporization and the decrease in air pressure in
the venturi, which causes a sharp temperature drop in
the carburetor. If water vapor in the air condenses when
the carburetor temperature is at or below freezing, ice
may form on internal surfaces of the carburetor,
including the throttle valve.

The reduced air pressure, as well as the vaporization of
fuel, contributes to the temperature decrease in the
carburetor. Ice generally forms in the vicinity of the
throttle valve and in the venturi throat. This restricts
the flow of the fuel/air mixture and reduces power. If
enough ice builds up, the engine may cease to operate.
Carburetor ice is most likely to occur when
temperatures are below 70?F (21?C) and the relative
humidity is above 80 percent. However, due to the
sudden cooling that takes place in the carburetor, icing
can occur even with temperatures as high as 100?F
(38?C) and humidity as low as 50 percent. This
temperature drop can be as much as 60 to 70?F.
Therefore, at an outside air temperature of 100?F, a
temperature drop of 70?F results in an air temperature
in the carburetor of 30?F.

 

[John_S]

Re: carb condensates really bad

Condesening usually doesn't cause problems, but icing can.

Is it happening after the engine is fully warmed up?

Do you have the exhaust cross-over blocked in the intake manifold (I am assuming you don't have vortec heads by the year) or using a thick heat isolator gasket to the carb?

 

[wire2]

Re: carb condensates really bad

It's not just 1 brand of carbs;

Reducing the pressure of a gas (air) absorbs heat. That's why an air tool will get chilled when in use.

Drawing air into an engine also reduces pressure, from atmosphere to the vacuum in the intake, past the restriction of a carb (or EFI) butterfly plate.

To counteract the chilling effect, I-4's and I-6's typically make the intake and exhaust manifold from 1 piece of cast iron. That allows exhaust heat to transfer to warm the intake above it.

Since a V engine has the intake manifold isolated from exhaust, there's a passage through the middle of the intake to carry hot exhaust from 1 head to the other.

If that passage is blocked by either corrosion, or using the wrong style of gasket, the heating effect can't take place, and the carb will be chilled, causing water vapor to condense.
If the air temperature is just above freezing, the carb may ice up.


EDIT
I see it's been pretty well answered by the time I finished typing.

 

[slag]

Re: carb condensates really bad

Not just edelbrocks, all carbs do it. Its from the venturi in the throat of the carb. Doesn't matter what type of fuel you use.

You should see an airplane carb, it forms ice on it at half power on 90 deg days.

One disadvantage of the float-type carburetor is its
icing tendency. Carburetor ice occurs due to the effect
of fuel vaporization and the decrease in air pressure in
the venturi, which causes a sharp temperature drop in
the carburetor. If water vapor in the air condenses when
the carburetor temperature is at or below freezing, ice
may form on internal surfaces of the carburetor,
including the throttle valve.

The reduced air pressure, as well as the vaporization of
fuel, contributes to the temperature decrease in the
carburetor. Ice generally forms in the vicinity of the
throttle valve and in the venturi throat. This restricts
the flow of the fuel/air mixture and reduces power. If
enough ice builds up, the engine may cease to operate.
Carburetor ice is most likely to occur when
temperatures are below 70?F (21?C) and the relative
humidity is above 80 percent. However, due to the
sudden cooling that takes place in the carburetor, icing
can occur even with temperatures as high as 100?F
(38?C) and humidity as low as 50 percent. This
temperature drop can be as much as 60 to 70?F.
Therefore, at an outside air temperature of 100?F, a
temperature drop of 70?F results in an air temperature
in the carburetor of 30?F.

However, this carb is sitting smack dab on a small gasket on top of the intake manifold which is mated to the engine which is operating somewhere between 140 and 180 degrees. On a boat, you wont get ice buildup due to heatsoak from your boat engine. On an airplane engine, with all the air rushing around it, I can see it happening.

I'd also tend to think most aircraft engines use diaphram style carbs. Is this not correct?

EDIT: I see this has already been addressed by at least 2 people ahead of me.

 

[LAC_STS]

Re: carb condensates really bad

Condesening usually doesn't cause problems, but icing can.

Is it happening after the engine is fully warmed up?

Do you have the exhaust cross-over blocked in the intake manifold (I am assuming you don't have vortec heads by the year) or using a thick heat isolator gasket to the carb?

I'll have to check into that. It's a new engine and this is how it came.

It happens anytime inrun the engine. Fully warmed or not. When I start it, by the time it warms up it's condensating.

 

[wire2]

Re: carb condensates really bad

After running 10 minutes or more, is the smaller passage in the center of the manifold quite warm to the touch? Careful, it may be well over 200? F

 

[LAC_STS]

Re: carb condensates really bad

After running 10 minutes or more, is the smaller passage in the center of the manifold quite warm to the touch? Careful, it may be well over 200? F

I will check that as soon as this rain stops and I go to the boat.