[scld1354]

Hello,

I have the dash taken all the way down to the firewall in my 67 GP. While everything is out, I am going through the under-dash AC box testing all vacuum and electrical pieces. As soon as everything checks out (or replacement parts are installed) the box is going back in and the dash will be put back together.

I have a couple questions about the vacuum part of the system. There is a vacuum "valve" on the controls (mounted to the dash) and another vacuum valve mounted to the top of the under-dash box.

I took the valve that is mounted on top of the box apart (because of how corroded the rest of the box is). The inside looks good, except there is no seal. It looks like cast metal with the mating surfaces machined flat, but no seals or gaskets. I checked with a hand vacuum pump and I can create vacuum, but the valve wont hold the vacuum very long in any position. The only info the service manual provides is that some vacuum lines are for vacuum and some vent to the atmosphere. Has anyone had one of these apart? Are they supposed to hold vacuum? Seems to me you wouldn't want any vacuum leaks at all, no matter how small.

The part looks very similar to this one: 1967-pontiac nos ac vacuum valve gm 1222686

In fact, that part is the one for the AC controls.