How can I boost vacuum?
Le Mans Master
Joined: Jan 2006
Posts: 9,192
Likes: 27
From: Boca Raton Florida
My 81 has a 1 gallon tomato can behind the front bumper that serves as a vacume can, it came that way. There is a 3 way check valve connected to the manifold behind the carb to preserve vacume reserve. When the car starts up you should have full system vac in about 15 oe 20 seconds. If not you have a leak some where or Bubbu struck and deleted the can. You definately need the can and check valve. install them and you should be good to go except in the case of a REAL radical cam.
Thread Starter
Team Owner
Joined: Aug 2006
Posts: 24,125
Likes: 15
From: Columbia Missouri
Originally Posted by SIXFOOTER
My 81 has a 1 gallon tomato can behind the front bumper that serves as a vacume can, it came that way. There is a 3 way check valve connected to the manifold behind the carb to preseerve vacume reserve. When the car starts up you should have full system vac in about 15 oe 20 seconds. If not you have a leak some where or Bubbu struck and deleted the can. You definately need the can and check valve. install them and you should be good to go except in the case of a REAL radical cam.
Thanks so much. Even if the stock can is the big heavy one in the bumper, would it hurt to add a coffee can style reserve for more -volume?
I'll double check the check valves, and check for more leaks.
Can those three way check valves be bought at Autozone / Oreilly?
Race Director
Joined: May 2006
Posts: 16,528
Likes: 53
From: Dayton, Ohio
Originally Posted by SIXFOOTER
My 81 has a 1 gallon tomato can behind the front bumper that serves as a vacume can, it came that way. There is a 3 way check valve connected to the manifold behind the carb to preserve vacume reserve. When the car starts up you should have full system vac in about 15 oe 20 seconds. If not you have a leak some where or Bubbu struck and deleted the can. You definately need the can and check valve. install them and you should be good to go except in the case of a REAL radical cam.
Pro
Joined: Aug 2005
Posts: 627
Likes: 1
From: Naperville IL
the lights should operate fine without the vac. reservoir, I know many people have taken it out to save weight and other potential vaccuum leaks. I've always been under the impression that the reservoir just acts as a buffer so you don't lose accessory vaccuum at WOT(not a likely time to be opening the lights or hitting the brakes) and also lets you close the lights for a little while after the engine is off.
how are you sure that don't have any leaks? I wouldn't assume anything when troubleshooting these cars
how are you sure that don't have any leaks? I wouldn't assume anything when troubleshooting these cars
Le Mans Master
Joined: Jan 2006
Posts: 9,192
Likes: 27
From: Boca Raton Florida
Originally Posted by Durango_boy
Thanks so much. Even if the stock can is the big heavy one in the bumper, would it hurt to add a coffee can style reserve for more -volume?
I'll double check the check valves, and check for more leaks.
Can those three way check valves be bought at Autozone / Oreilly?
I'll double check the check valves, and check for more leaks.
Can those three way check valves be bought at Autozone / Oreilly?
Measure the actual vac signal you have at idle and let us know what you have, a vac gauge should be under $20 and is essential to old car work.
Le Mans Master
Joined: Jan 2006
Posts: 9,192
Likes: 27
From: Boca Raton Florida
Originally Posted by dwncchs
Sixfooter is that in addition to the big bumper tube or is that all you have?did they do away with the bumper thing?
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Drifting
Joined: Mar 2006
Posts: 1,526
Likes: 2
From: Oak Ridge NC
Originally Posted by Durango_boy
Thanks so much. Even if the stock can is the big heavy one in the bumper, would it hurt to add a coffee can style reserve for more -volume?
I'll double check the check valves, and check for more leaks.
Can those three way check valves be bought at Autozone / Oreilly?
I'll double check the check valves, and check for more leaks.
Can those three way check valves be bought at Autozone / Oreilly?
I don't know if autozone has them, but you can get one at ecklers.
The canister under the fender is a reserve. The reserve is used to raise or lower the headlights after the motor is off. You don't need another reserve canister.
Buy yourself a vacuum tool (the type used for vacuum bleeding brakes-cheap at autozone) and start checking the vacuum hoses to find the leaky hose and replace it. Check the actuators as well. Don't forget that the vacuum hoses also go to switches underneith the dash. Might want to get yourself a vacuum routing/troubleshooting diagram ($12 at ecklers).
Once you fix the leak, your headlights/wipers should work satisfactory with your new engine as long as your pulling above 10" as corvette engineering stated.
Thread Starter
Team Owner
Joined: Aug 2006
Posts: 24,125
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From: Columbia Missouri
Originally Posted by chris73cpe
how are you sure that don't have any leaks? I wouldn't assume anything when troubleshooting these cars
I didn't assume that. when I started having problems with my headlights...I started checking vacuum tubes. I did indeed inspect the tubes inside, as well as all underhood tubes. I did not check the valves, but I checked all tubes.
And because I know your next statement will be you can't tell just by looking, all the junctions close to the engine were tested with brake cleaner. I sprayed brake cleaner at any junction of vac hoses and listened for any change in RPMs. If you have a leak, the engine will suck it in, and the RPMs jump a little.
I found no leaks through the whole process. Again, I did not check the valves.
Also, the booster was fine, as well as the vac on the dist. and mine has a check valve inline with it.
Race Director
Joined: May 2006
Posts: 16,528
Likes: 53
From: Dayton, Ohio
Originally Posted by SIXFOOTER
Its in place of the bumper deal Dw, I guess they changed the design. Mine has a 1 gallon Tomatto can mounted on a steel bar that is connected between the bumper plate and the lower radiator mount.
Race Director
Joined: May 2006
Posts: 16,528
Likes: 53
From: Dayton, Ohio
Originally Posted by Durango_boy
I didn't assume that. when I started having problems with my headlights...I started checking vacuum tubes. I did indeed inspect the tubes inside, as well as all underhood tubes. I did not check the valves, but I checked all tubes.
And because I know your next statement will be you can't tell just by looking, all the junctions close to the engine were tested with brake cleaner. I sprayed brake cleaner at any junction of vac hoses and listened for any change in RPMs. If you have a leak, the engine will suck it in, and the RPMs jump a little.
I found no leaks through the whole process. Again, I did not check the valves.
Also, the booster was fine, as well as the vac on the dist. and mine has a check valve inline with it.
And because I know your next statement will be you can't tell just by looking, all the junctions close to the engine were tested with brake cleaner. I sprayed brake cleaner at any junction of vac hoses and listened for any change in RPMs. If you have a leak, the engine will suck it in, and the RPMs jump a little.
I found no leaks through the whole process. Again, I did not check the valves.
Also, the booster was fine, as well as the vac on the dist. and mine has a check valve inline with it.
Last edited by ...Roger...; Aug 20, 2006 at 11:08 PM.
Thread Starter
Team Owner
Joined: Aug 2006
Posts: 24,125
Likes: 15
From: Columbia Missouri
Originally Posted by dwncchs
Like BBC said get a vacumn pump and gauge combo -with a vette you will use it and when you ask for help on this forum you will be refered to this pump or gauge.It will be worth the money.Check all vacumn units individually.The brake clean trick is not good enough for this.
I plan to get one of those combos today I think. The vacuum problem is not a huge issue at thos point since I am dealign with my frig'n taillight and signal problem, but I know they will be good to have in the future.
Drifting
Joined: Mar 2006
Posts: 1,526
Likes: 2
From: Oak Ridge NC
I went back to your original post. Are you currently runnig the car?
If so, a quick way to check if your vacuum system may have a problem is to cap the vaccum port on the intake manifold. Let the car warm to idle. Disconnect the main hose for your vacuum system and cap the intake port. If there is a noticibly smoother idle with the port caped, then the system feeding the headlights/wipers is probably leaking.
If so, a quick way to check if your vacuum system may have a problem is to cap the vaccum port on the intake manifold. Let the car warm to idle. Disconnect the main hose for your vacuum system and cap the intake port. If there is a noticibly smoother idle with the port caped, then the system feeding the headlights/wipers is probably leaking.
Thread Starter
Team Owner
Joined: Aug 2006
Posts: 24,125
Likes: 15
From: Columbia Missouri
Originally Posted by SmokinBBC
I went back to your original post. Are you currently runnig the car?
If so, a quick way to check if your vacuum system may have a problem is to cap the vaccum port on the intake manifold. Let the car warm to idle. Disconnect the main hose for your vacuum system and cap the intake port. If there is a noticibly smoother idle with the port caped, then the system feeding the headlights/wipers is probably leaking.
If so, a quick way to check if your vacuum system may have a problem is to cap the vaccum port on the intake manifold. Let the car warm to idle. Disconnect the main hose for your vacuum system and cap the intake port. If there is a noticibly smoother idle with the port caped, then the system feeding the headlights/wipers is probably leaking.
Good idea. I'll get to that one too. Sounds like a good test.
