Vacuum Requirements
Thread Starter
Burning Brakes
Joined: Nov 2006
Posts: 893
Likes: 7
From: Orange Park Florida
Vacuum Requirements
Can anyone tell me the vacuum pressure needed to operate the AC/heater/fresh air vents on my 72 Stingray? I replaced the console on the car and may have knocked loose a vacuum hose. I want to apply a constant vacuum on the main feeder (from the engine) and find the problem - without having to constantly run the engine.
Jim
Jim
Racer
Joined: Feb 2007
Posts: 457
Likes: 2
From: Tucson Arizona
I understand what you are going to do, 5-10 in/Hg will do it. The problem arrises when you don't really know how much vacuum the engine is producing. With a constant vacuum, you can troubleshoot and get the under dash stuff working, but if you have manifold problems, or leaks under the hood, the stuff stil won't work.
Burning Brakes
Joined: Feb 2006
Posts: 1,024
Likes: 1
From: AL
you can use a "mighty-vac" for testing the A/C vents. when everything is working properly, it takes just a few pumps to cycle the A/C-heater actuators.
headlights or brake booster are another story; the "mighty-vac" is too small. having a constant vacuum source like another car or an air vacuum pump like, http://www.toolsource.com/vacuum-pump-p-96301.html, makes troubleshooting much quicker.
headlights or brake booster are another story; the "mighty-vac" is too small. having a constant vacuum source like another car or an air vacuum pump like, http://www.toolsource.com/vacuum-pump-p-96301.html, makes troubleshooting much quicker.
Race Director
Joined: Apr 1999
Posts: 11,520
Likes: 13
From: CORVETTE 77 385 C.I. TEXAS
I would run the engine since it should only take a few seconds to find a disconnected hose. Try pressing the vac. switch together.
A vac. pump can be made by adding a hose to an air pump intake.
The vac. required by the headlights is minimal [(under 5) also arrived at independantly by Markus (zwede)].
A vac. pump can be made by adding a hose to an air pump intake.
The vac. required by the headlights is minimal [(under 5) also arrived at independantly by Markus (zwede)].
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,118
From: Crossville TN
Intake manifold vacuum, with a healthy engine and a mild cam, should make 15 in. Hg or more. You'd like to see 17-21, if everything was sealed and working right. The headlights can start to malfunction around 10 in. Hg, or so. To see what the engine ALONE can do, pull all of the hoses off the vacuum block (on the intake manifold) and seal all but one off; then hook your vacuum gauge to the remaining connection. Start engine and let idle. Read the vacuum gauge. Use this number as your "baseline" reading. Ideally, you want the vacuum level to stay within 2" Hg of the baseline reading WITH ALL THE VACUUM SYSTEMS CONNECTED. If it doesn't, you have one or more leaks and need to find and correct them. Add systems back, one at a time, to find the leakers. Good luck.
