new carb, Getting really cold on intake. Need advice

C

crotex

Junior Member
I have been having troubles with the Zenith carb on my 31 Model A and I ended up getting a Tillotson carb from a friend today. I got it on and now I have a crazy whistle noise coming from somewhere I can't fine and also the carb is getting so cold when running it has condensation dripping off of it as well as the intake. Please forgive me if this is dumb stuff to ask but I am new to this and I would like to get some advice on how to fix this problem. Another thing is that the motor will not stay running unless it is fully choked.
 
what are all of the places I should check out? I chaged the base gasket with a new one and snugged the two bolts down pretty tight.
 
spray oil (fluid) to the gakets while engine is running
once sealing the leak, idle should change....
greetings christoph
 
If it is a used tillotson it could be in the carb itself . Should maybe rebuild it . Did you have the same problem with the zenith?... one thing for sure it is definatly a vacuum leak
 
Tilly's (and others) often leak where the throttle plate shaft pierces the updraft of the barrel. Mine whistled, had it rebuilt (Zenith and Tilly), no whistle, no updraft extra O2 to mess up the mixture. Vendors carry an inexpensive kit to seal the shaft, but MAKE SURE YOU DO IT RIGHT. I did it wrong twice and had the throttle stick wide open until I went to Neutral, under the hood, wrenched back the throttle horn.

Why is it cold and dripping? I'm stumped. Are you using freon for fuel? The Flux Capacitor? Leaking fuel all over the carb (bring a Fire bottle, a big one) and get that fixed.

Fuel bowl set too high can lead to gushes of fuel back through the intake. Full Choke in order to run is just your leaky Carbs way of saying she's getting far too much air for the stoichiometric fuel-to-oxidizer ratio to work it's natural charms.
 
crotex said:
what are all of the places I should check out? I chaged the base gasket with a new one and snugged the two bolts down pretty tight.
Click to expand...

Check the flange on the tilly that attaches to the manifold. The have been know to warp.

Now you will tell us what works this time won't you? Your solving of the electrical problem is still a mystery to us.
 
crotex said:
what are all of the places I should check out? I chaged the base gasket with a new one and snugged the two bolts down pretty tight.
Click to expand...
All the above is good advice but, here is the problem. The tilleys are made out of pot metal and as such are prone to the mounting flange warping. You have to have a light touch to tighten the nuts. A friend of mine used to, as a normal habit, tighten the carb before a tour. He couldn't figure out why his car would run so bad after a while. I used a file to flatten the flange and, took his 1/2" wrench away from him so, no more problem. Remove the carb, sand on a very flat surface or, use a large mill ******* file to flatten the top of the carb mount and the whistle will go away. Just be sure you don't tighten the nuts too tight and warp it again. The icing is also related to this problem since the carb is pulling cold air in above the rear intake, where the exhaust can provide warm air to prevent this.

You have to run full choke because you are getting too much air and have to choke it to pull enough fuel in to regulate the mix.

Hope this helps
 
Be very careful mounting any carburetor to make sure it's mating to the manifold straight with no binding. It's easy to break an ear off your intake manifold. Does this sound like experience speaking??
 
I'll bet the top flange is slightly wrapped, Tilly's are famous for this. No matter how hard you try to seal they still leak air. The fix is to flatten out the top flange, It can be milled flat or place a piece of wet dry sand paper on a flat granite surface plate and sand flat in a figure eight rotation motion.
 
The icing is due to a pressure drop. The air flowing past the throttle plate goes under a large pressure drop, thus cooling the air. This icing is most noticable on cold damp days. My Alis Chalmers WD does the same thing until the engine is real warm.

My air compressor is outside and when I try to sandblast when the temp is about 35 to 40 degrees the cold damp air will often freeze in the line due to the pressure drop when I start using the blaster. Thus no sandblasting unless the temp is over 40*.
 
Tom is right (as usual). The pressure drop and resulting temperature drop is caused by the air flowing through the venturi just upstream of the throttle plate. Icing will form around the throttle on days when the ambient temp is just above freezing and the humidity is relatively high. Carburetted aircraft have carb heat systems where exhaust is routed to the carburetor to prevent (or to melt!) carb icing. My Farmall Cub used to do it but I fashioned a baffle in front of the carb to prevent cooling air from blowing over it.
 
You don't need an air leak to get carb. ice. Old 182 explained it exactly. Carb ice is caused by low pressure in venturi and will show itself mostly on humid and cool days. All pilots are very familiar with this. Happens to cars too.
 
This icing/cooling effect is why most early cars had heat risers in the exhaust manifold, to direct the hot exhaust gas through passages in or next to the intake manifold. Later cars had tubes going from the air cleaner to tinwork around the exhaust manifold to run hot air through the carb when the engine was cold. Of course, the Denny-Dimwits would rip all this stuff off, thinking they were making their engine run better!
 
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