Next to the firewall, there are 2 or 3 small vacuum hoses that are now brittle and snapped. See the image below with all the red arrows.

First, what are they used for? Looking to replace them so what is the part number, or what are they called? Thanks in advance.

 

when they transition to being larger, where are they going? behind your left hand....

 

does vacuum advance work? headlights? heater vents? generally vacuum problems are fixed with generic hose and the occasional T or splice fitting. once your car is so nice that these non-oem hoses start to stick out, then you worry about originality.

 

Everything is now working. Lights, vents everything. I just noticed that these small wants are brittle and figure since I just replaced all the vacuum hoses I should replace these. Just not sure what they are called and where to find them.

 

On our 1968 C3 I went to Dr.Rebuild out at Carlisle at the annual Corvettes@Carlisle. He sold me a beautiful bag Full of Color Coded vacuum hoses to replace every inch on my 1968 427 Convertible with a 4 speed. The kit also had all the new Tees and check valves for the system to be "complete" when finished the installation. He also sold me a chart that has the entire car hose layout with corresponding colors so you have a vacuum "layout" which invaluable if you have vacuum issues.

For the 1968 model year the Corvettes kit included literally multiple bags of different size and length Hoses. For the next twenty five plus year those headlights "jumped" to attention as do the wiper doors. I was a novice back when I needed this done so I had Tony's Corvettes in Gaithersburg, MD. do the job for me. Tony and his crew all "knew" the original routing the vacuum lines and were able to make it work and function like"New" for a long time. On a 1968 Corvette there are dozens of hoses and they literally run "all over" the place. I came out the winner having a professional do the job right the first time. Twenty years out it was holding a vacuum for weeks.

You "should" have an under-hood sticker of the emissions layout on the particular engine. Those are really helpful on the rigid vacuum lines. These engine expose the vacuum lines to a lot of heat and they break down. The hose on a reel is cheap and easy to replace. I keep it and the stuff to fix the original stiff vacuum lines. Your goal should be "no vacuum leaks" as they negatively affect the engine whether fuel injected or not. I found four or five on my C4 right after I bought it. It sure ran a whole lot better afterwards.

 

One hose goes from the the manifold to a plug on the box at the firewall.



The second hose goes from the tee to behind the distributor. But I can't see where it attaches. Any ideas where it attaches?

 

Someone mentioned it might be the vacuum source for the HVAC controls. Still trying to see where that plugs in. Any suggestions?

 

Those are definitely your HVAC control vacuum lines. Don't have a photo handy to post. Shouldn't be very hard to get a chart for your year however.

 

So these go through the firewall to the AC control. Where does it enter the firewall? Center, left, right, can't seem to find that spot?

 

OK. one step at a time here. in your first photo (Post one) you have you finger on the vacuum line that is the "Feed" to the switch. it also "T's" off behind the dash and supplies vacuum to the hot water shut off switch. it enters the dash below and on the right hand side of wiper motor. Very hard to see with the wiper motor in position. Then 2 lines come back out of the firewall out of a hump in the firewall just below the wiper motor far right attaching stud. There should be a wire clip there as well. One of those 2 lines then enters the wiper tray just below the hood alarm switch. or just left of the hump for the vacuum wiper door actuator if you have a early car. The hump is still there in newer cars but it's just a hump. The line that goes into the wiper tray continues to the right side of the car and disappears behind the cowl vent screen. Behind that screen is the vacuum actuator that closes off outside air when you have the control in the Max Air setting. the other of the 2 lines goes to the hot water shut off in the heater hose. It is usually pale yellow or white, or black with a white stripe.

 

Maybe this will help. In this diagram it shows all 3 going into one grommet. Most likely the one straight below the right hand (as your sitting in the car) wiper motor mounting stud.
My car is as described above however. I just went through and got all my HVAC system working a week ago.

 

What year is your car ? The vacuum systems did indeed change over the years.

 

Looks like he has an 81. mine is an early 77. the diagram I put up is 78-82. thought it would help him.

 

1981

 

I'd would remove the Air cleaner to expose as much area as possible. It seems the hoses may be Emission related. What work or modifications have been done if any to your car that may have eliminated the hose(s) use ? Here are some links that may lead to discovery.
https://www.corvetteforum.com/forums...gram-help.html
http://repairs.willcoxcorvette.com/1...st-no-complete

If you enter your query into the CF C3 Tech or General section and search you may find what is you are looking for. It is always best to have an Assembly Manual for your year Corvette, it is money well spent.

Good Luck