1985 C-30 454 Vaccuum line to AC/Heater Control

[DonnyLee]

Hi Guys, working on getting my AC vacuum line source hooked back up to the control panel on the dash 1985 454. The trouble I have is it appears the Vacuum line feed has been cut off coming through the fire wall and have a small stub of what I would describe as the size on like a plastic manual oil pressure size vacuum line size that is black cur off by a Former Owner. What is this suppose to look like? Is it possible to splice onto the small stub that is protruding out of the firewall? Or am I better off running a new line to the temp control. I guess I am asking is where would I either source a new correct line, or the bits needed to splice this, and then connect to the QJ Carb? And where would I source them? Thanks in advance for you input/help!

 

[YakkoWarner]

Mine broke off in about the same place (1989 w/454 instead of 1987 but don't think the HVAC controls changed much). I just used some small rubber vacuum line that fit snugly over the broken end - if you have enough of a stub sticking out maybe a little shrink wrap over it to help seal up. The previous owner may not have cut it - that plastic tubing gets really brittle over time, and with the temps in the engine bay of a 454 it eventually just breaks.

Ideally replacing the whole line would be the "right" way to repair it but would mean major tear-apart inside the cabin behind the dash. You can just use rubber vacuum line to go from the stub to the vacuum source on the intake (usually it involves a T connection of some sort and another line going over to the vacuum reservoir). When those plastic tubing lines break I always just use rubber vacuum hose, so much easier to work with.

 

[75gmck25]

That is called hard/rigid vacuum line, and it is sold in two sizes. You can easily splice it with short sections of rubber line. This is one example https://www.dormanproducts.com/p-6924-47417.aspx .

They used to stock it along with the other Dorman products, but I haven’t looked for it recently. I also can’t remember exactly which of the two diameters is the best match to the original GM hard line.