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I am trying to figure out the vaccum system on my C3 1981 and could use some help.
The scenario is that my corvette did have its engine replaced with what i believe to be an early 70s C10 engine with electronic ignition and edelbrock intake and carb. It also did have its vaccum operated headlights replaced with Monza style fixed headlights.
The situation is that the heater/AC vents inside the car do not work and i think i have found the problem.
Question is how this vaccum system now SHOULD look like in order to get the heat/AC to work inside. Pictures attached:
Seems to be the manifold to power booster vaccum line with filter. I think this is ok?
This one i am not too sure about. Just a single line between distributor and carb with a plugged t-section halfway?
And then there's this t-section going into the firewall without anything connected to it? I assume this should get its vacuum from a source somewhere to go to the vacuum switch inside? Where should i get this source from?
I have an 81 vette also the main vacuum line comes off the intake manafold on passenger side or just behind the carb on the right side that is the baby that controls almost every thing. on mine i have manual control switches for heat and air inside on the control panel
I made a mistake my main vacuum is the same as yours only mine is a tee going to. my head lights and brake booster I do not see on mine any tubes going into the fire wall my heat works great but not my air
I have an 81 vette also the main vacuum line comes off the intake manafold on passenger side or just behind the carb on the right side that is the baby that controls almost every thing. on mine i have manual control switches for heat and air inside on the control panel
So the hose coming from the carb is the source? In that case i could just connect a new hose to the plugged t-section and connect it to the other t-section near the firewall? Would that work?
on my vet i have an HEI distributor with out a vacuum advance i have been told i need a vacuum advance as of right now i have 2 many iron in the fire but looked it up and they suggest to the intake vacuum with a manual trans. to the carb with a auto trans. my suggestion do a web search for vacuum line hook up for your given year and go from there
From: Some days your the dog and some days your the hydrant.
Royal Canadian Navy
Originally Posted by aalmans
So the hose coming from the carb is the source? In that case i could just connect a new hose to the plugged t-section and connect it to the other t-section near the firewall? Would that work?
Short answer, yes. But the vacuum line for the dist'r might be ported vacuum. I'm not familiar with that carb. You need manifold vacuum to do it proper.
Short answer, yes. But the vacuum line for the dist'r might be ported vacuum. I'm not familiar with that carb. You need manifold vacuum to do it proper.
It's connected to the lower of the two so i assume this is manifold vacuum. I will try it out!
And then there's this t-section going into the firewall without anything connected to it? I assume this should get its vacuum from a source somewhere to go to the vacuum switch inside? Where should i get this source from?
Thanks!
Hmm, i figured out one more issue. The vacuum lines going into the firewall are just cut off on the inside !
Where should they lead to? The vacuum switch? What else? There seems to be a hose missing there as well?
Trying to figure this vacuum system our but am not very succesfull at this point.
You need vacuum hoses for the headlights and the heater/a/c controller.
I do not have vacuum operatd headlights anymore. The PO switched them to static Monza style rectangular headlights. I guess this is when he cut off all vacuum lines including the ones required for HVAC to work.
Where does the vacuum selector switch in the center console gets its vacuum from normally?
From: Some days your the dog and some days your the hydrant.
Royal Canadian Navy
My '76 gets it from a very small diameter vacuum hose which is dark brown or black. I thought it was a 16 gauge wire when I first noticed it wondering what it was for.
I believe the vacuum nipple on the LEFT side of the carb is "ported" vacuum. The nipple on the right is "manifold" vacuum. Move the distributor vacuum hose to the right side.
There are many resources for how the vacuum system works. Willcox and Paragon just to name a couple. I would recommend you study these before attempting a shotgun fix. The system may look very complicated but when you look at it in total, it’s pretty straightforward. Spending a couple hours learning the fundamentals will pay big dividends down the road when other problems surface (and they will).
Hmm, i figured out one more issue. The vacuum lines going into the firewall are just cut off on the inside !
Where should they lead to? The vacuum switch? What else? There seems to be a hose missing there as well?
Trying to figure this vacuum system our but am not very succesfull at this point.
Any pointers anyone? Thanks!
I figured it out. The hoses that were cut off in the picture above turned out to previously have gone to the headlight switch but since the PO replaced those with stationary Monza style rectangular headlights these hoses were no longer required.
The black small diameter hose going into the vacuum selector was not connected to anything and the black with white small diameter hose was not connected to the water valve. Once i connected everyting as it should and connected the small black vacuum hose to the manifold vacuum port on the carb everything started to work including ventilation and heat!
Only question i have left is if i should put a vacuum filter just before the carb to be sure?
Need some help with vacuum system
