Farm Equipment - Carb Question

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Carb Question

Printed From: Unofficial Allis
Category: Allis Chalmers
Forum Name: Farm Equipment
Forum Description: everything about Allis-Chalmers farm equipment
URL: https://www.allischalmers.com/forum/forum_posts.asp?TID=209244
Printed Date: 06 Dec 2025 at 3:37pm
Software Version: Web Wiz Forums 11.10 - http://www.webwizforums.com

Topic: Carb Question

Posted By: Gary Burnett
Subject: Carb Question
Date Posted: 06 Dec 2025 at 11:33am

What causes the throat of the carb where it bolts to the intake to frost up?

Replies:

Posted By: steve(ill)
Date Posted: 06 Dec 2025 at 12:21pm

the velosity of the air ( or expansion) going thru it... Like an air conditioner spraying freon thru an orifice.. as it EXPANDS it gets very cold..

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Like them all, but love the "B"s.

Posted By: plummerscarin
Date Posted: 06 Dec 2025 at 1:53pm

Venturi effect. As air flows through the carburetor the reduced diameter causes the air velocity to increase which reduces pressure. This pressure drop has a cooling effect. Adding fuel to the mix cools it even. Moisture in the air condenses and shows as frost on the carb. This frost can build up on the inside reducing throttle opening and causing poor engine performance especially at WOT. Or something like that.
I had that issue roading the 170 home in January a couple years ago