My car will start run well for a few munites warm up and then it starts
bogging and dies. When looking at the carb it looks like someone is melting
dry ice (white vapors).

Any advice?

 

That is a mixture of burned fuel smoke and unburned fuel vapour. Or maybe your carb is icing.

 

how does one prevent iced carbs?

 

I think a little starting fluid may help. Mine (maybe all nikki carbs) has a sub-zero starting assist system. It injects a mixture of 90% ethyl glycol antifeeze and 10% water into the carb when it is below 0 to prevent icing.

 

Leave the stock exhaust manifold and heat riser setup in place, leave the coolant passages to the intake manifold open, don't drive where it gets humid and cold, that's about it.

Buy a can of windshield de-icer. It's a blend of methanol and other nasty stuff in an aerosol can. When you set out in the morning and the car runs rough and then dies 5 minutes after you start driving, pop the hood, pop the air cleaner lid off, and spray the de-icer into the primary carb venturis (the ones with the choke plate over them). If you want to aim it at something, aim it at the boosters, which are the multi-ringed thingies hanging in the middle of the venturis. Now, put the lid back on and the hood back down, go back into the car, smile and wave at the people flipping you off, light a smoke if you want... basically wait about 30 sec to a minute after you spray. Then start the car and finish driving to work.

The de-icer works to melt the ice and also is great as a starting ether to re-prime the engine. While it works pretty much on contact, waiting a little while allows engine heat to soak up to the carburetor to prevent it from happening again. (Don't wait too long or it'll all cool off again)

One can of de-icer lasted me all winter, and that included using it to clear the ice out of the door locks and off of the weatherstripping - my doors liked to freeze shut, a few times I had to go in through the sunroof, good thing I leave it open eh?

 

That would really suck. Carb's are designed for Southwest were its dry and warm. Or really were ever its very dry. This is partly why fuel injection is the only way to go really....the fuel doesn't get a chance of becoming a refrigrant below the butterfly's because it injects it right near the ports. Unfortunetly gas is a refirigrant when you pull some vaccum. I hate cool humid days too. Right now in MN, its going to dip below zero F, however the humidity is always low when its this cold.

I hate the 35-60range when ever its even mildly humid. I own a Mikuni carb setup and it tends to frost up on the outside of the carb the most in this range, and that tells you whats happening inside of it. The key to getting around this problem is varing the throttle contantly. This makes it hard for icy spots to build up in the carb. Going up around full open throttle and varing from normal crusing throttle position pulls out the icy crap and is the only way to avoid it if you live were its always humid and cool. Except if you have the stock air box/with exhuast manifold heater tube/and coolant heated intake.

 

Hell, my intake and carb ice over in the middle of the summer.