Carb heat

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Carb heat

Post by jmcanni » Tue Dec 08, 2009 1:57 pm

Wondering if I should have a heat box on my lycoming o360 would like to use it to do some ice fishing and goose hunting dont want to get stranded. lol!! Live in Nebraska so temps could be below zero. And also where to find one mabe used.

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Re: Carb heat

Post by Whitebear » Tue Dec 08, 2009 1:58 pm

Fairly easy to do, and not a bad idea for up there either.

Remember you will get slightly lower RPMs and a bit less HP with the carb heat on because the heated air is less dense than the normal outside air.

I would make a valve or vane to select normal or carb heat, similar to what an airplane has. It does prevent carb icing in the planes for normal operation, however they don't generally fly into known icing conditions without some other options as well.

If you have a water separator/filter you might consider some heat tape for it cause you don't want separated water freezing in the flow. I would also consider a heated fuel tank for the same reasons. we don't check for condensation water in the tanks before every run like airplane folks do, and we don't have the instant drains to get rid of it so likely some will always be there. You should be able to get heat tape at your local A&P shop at the airport. or check Aircraft Spruce, they "might" have it.

Just thinking out loud here some, I used the heat tape on my truck in Alaska with great results, also a heated battery blanket. In sub zero temps you want to change to a lighter viscosity engine oil as well.

There are several folks from the Great White North here who will likely chime in on what and how they do it. Keep checking back.
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Re: Carb heat

Post by Canuk » Tue Dec 08, 2009 4:17 pm

I have an 0360 with a Holley carb that I run in cold temps. I don't have a heated intake and I haven't had any problems. The carb and intake manifold will ice up about 1/4" thick on the outside, but I haven't seen any ice looking down the throat of the carb, I suspect there is so I change my oil often.
On humid days it can build up on the carb linkage enough to stop the throttle plates from seating all the way down onto the low idle stop. I have a small piece of rope tied to the linkage that I can manually pull just in case I need to give it a bit of help.

I deal with customers iced up fuel systems on outboards/snowmobiles all the time.
There are a number things we need to do to avoid having problems:

- add approx 4-6 oz of Isopropyl Alcohol per 5 gallons of fuel
- don't store fuel for more than two weeks and keep the tanks full, including the boat tank. If you can see ice on the outside of a partially full fuel tank, you will have an equal amount of ice on the inside of the tank.
- gerry cans and fuel tanks will get condensation in them if they are exposed to changing temperatures. Direct sunlight after a cold night is a sure killer.
- change the water separator filter often. I keep a few spares and change them every few days, I dump them and then dry them inside and put them back on a week later.
- never ever use Ethanol fuel, without getting technical about it.....everybody who has tried it has problems eventually, often complete powerhead failures. Here in Canada Sunoco has ethanol in all their fuel grades, all the rest of the oil companies do not put ethanol in their premium fuels.
- For my own equipment I run all the fuel through a good water separator funnel (Mr Funnel), it is amazing how much condensation it catches and I am very very careful at trying to prevent it.

In spite of all these pains in the butt it is still a constant challenge.

hope this helps


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