Q-jet Q.

[Geargrinder]

I just pulled the stock air cleaner off of my Q-jet ('84 3/4T Burb) to put on an aftermarket open style. I had one vac. line that went to a little vac. diafram that had a rod going to the top butterfleys on the 2nds(?). Any one know what that is for? The secondarys seem to still be working fine, but I am wondering about that line.

 

[dyeager535]

If just one hose from that diaphram to the air cleaner, then it is probably nothing more than a breather/vent line. If it's to the carb body then it was probably doing some actual "work".

 

[Geargrinder]

Well...... It went to a 3 port switch in the air cleaner, and the other side of the switch went to a line that was "Y"ed into the carb and a thermal switch in the front of the manifold.

 

[dyeager535]

Sounds like at least part of THERMAC to me, but I've never seen a 3 port switch in the air cleaner. Doesn't mean they didn't exist, just not familiar with that setup.

Mine had a temp switch in the air cleaner, but one vacuum line from the carb to the switch in the air cleaner, and one from that switch to the THERMAC.

The emissions label (if even still present) will tell you what each line goes to/comes from.