Vacuum hose on choke? not talking about choke pull-off
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Joined: Sep 2001
Posts: 400
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From: Buffalo, N.Y
Car: 1983 Z28 Clone
Engine: 350
Transmission: TH350
Vacuum hose on choke? not talking about choke pull-off
Hello I have a 78 q-jet .....now i dont know if this tube coming off of the choke housing is some sort of heat collector or some kind of vacuum hose connection. I'm not talking about the choke pull-off that connects to the top portion of the carb on the left hand side. MY question is what do i connect this too??? thanx
Rob
Rob
Joined: Mar 2000
Posts: 43,187
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From: Littleton, CO USA
Car: 82 Berlinetta/57 Bel Air
Engine: L92/LQ4 (both w/4" stroke)
Transmission: 4L80E/4L80E
Axle/Gears: 12B-3.73/9"-3.89
You have the famous "hot air" choke.
A tube is run via a plate bolted to a boss on the intake manifold into the exhaust cross-over passage of the manifold (the April 2002 CHP magazine that arrived in the mail today has a picture of a manifold with that boss on page 56 - the boss in front of the EGR boss). A small amount of air is allowed to flow through that tube via a small vacuum passage in the choke thermostat housing to manifold vacuum, which is warmed by the exhaust gases as it goes through the tube. The warm air then warms the choke thermostat, causing it to open the choke butterfly as the engine warms up.
If you don't have a manifold with that hot air boss, and don't have the tubes required to make it work, you can convert it to electric very easily. The thermostats are the same size, and just put a cap on the hose nipple on the housing.
A tube is run via a plate bolted to a boss on the intake manifold into the exhaust cross-over passage of the manifold (the April 2002 CHP magazine that arrived in the mail today has a picture of a manifold with that boss on page 56 - the boss in front of the EGR boss). A small amount of air is allowed to flow through that tube via a small vacuum passage in the choke thermostat housing to manifold vacuum, which is warmed by the exhaust gases as it goes through the tube. The warm air then warms the choke thermostat, causing it to open the choke butterfly as the engine warms up.
If you don't have a manifold with that hot air boss, and don't have the tubes required to make it work, you can convert it to electric very easily. The thermostats are the same size, and just put a cap on the hose nipple on the housing.
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