head light(s) lift/raise @ acceleration
Thread Starter
5th Gear
Joined: Jan 2018
Posts: 5
Likes: 0
head light(s) lift/raise @ acceleration
Hello to all. My question pertains to the headlights on my 72 vette. While accelerating (RPMs about 3500ish) the drivers side (and occasional the passengers side) headlight will raise up, but when I come off of the accelerator, the headlight(s) will go right back down. It doesn't happen all the time, and it seems to be when I am accelerating from low speed, Has anybody else experienced this? Can anybody direct to a possible cause?
Race Director
Joined: Oct 2008
Posts: 19,257
Likes: 1,678
From: Long Island
Double check the check valve on the vacuum line from the carb to the vacuum system.
I would also check to see if the vacuum tank is leaking.
When you are near wide open throttle position there is little vacuum in the vacuum control system if the check valve is bad.
I would also check to see if the vacuum tank is leaking.
When you are near wide open throttle position there is little vacuum in the vacuum control system if the check valve is bad.
Thread Starter
5th Gear
Joined: Jan 2018
Posts: 5
Likes: 0
Much thanks. I got the car a couple of months ago (its my 1st vette), so I'm "learning" it. thank you again.
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,118
From: Crossville TN
When you accelerate (WOT), engine vacuum goes very low. If vacuum system components have leakage, 'funny' things can happen to wiper door, headlamps, etc. The vacuum reservoir tank is there to help maintain vacuum level on those systems during WOT use. That check valve separates the vacuum reserve tank from the engine so system vacuum will not drop significantly.
It is also possible that the seals in the headlamp vacuum relays are very worn/hard and have leakage.
It is also possible that the seals in the headlamp vacuum relays are very worn/hard and have leakage.
Last edited by 7T1vette; Jan 13, 2018 at 09:01 AM.
Le Mans Master
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Melting Slicks
Joined: May 2015
Posts: 2,365
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From: Cape Girardeau Missouri
Here's an excellent thread about our headlamp doors.
It's very possible that the check valve (installed after the filter) is nearly all of the problem. If it fails vacuum in the small volume control portion of the system will drop very quickly during wide-open throttle. When this happens the doors will begin to open but the vacuum tank will loose its charge quickly. Once engine vacuum returns to normal the doors will close and everything will seem normal.
It's very possible that the check valve (installed after the filter) is nearly all of the problem. If it fails vacuum in the small volume control portion of the system will drop very quickly during wide-open throttle. When this happens the doors will begin to open but the vacuum tank will loose its charge quickly. Once engine vacuum returns to normal the doors will close and everything will seem normal.
Instructor
Joined: Aug 2017
Posts: 180
Likes: 24
From: Jacksonville Florida
How to identify and test all the components:
http://www.corvette-101.com/vacuum.htm
http://www.corvette-101.com/vacuum.htm
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Thread Starter
5th Gear
Joined: Jan 2018
Posts: 5
Likes: 0
When you accelerate (WOT), engine vacuum goes very low. If vacuum system components have leakage, 'funny' things can happen to wiper door, headlamps, etc. The vacuum reservoir tank is there to help maintain vacuum level on those systems during WOT use. That check valve separates the vacuum reserve tank from the engine so system vacuum will not drop significantly.
It is also possible that the seals in the headlamp vacuum relays are very worn/hard and have leakage.
It is also possible that the seals in the headlamp vacuum relays are very worn/hard and have leakage.
Team Owner
Joined: Jun 2001
Posts: 23,381
Likes: 1,067
From: Virginia USA
http://repairs.willcoxcorvette.com/
Race Director
Joined: Apr 2009
Posts: 19,294
Likes: 2,754
From: Charlotte NC
Also there is a black plastic shield installed in front of your headlights on a 1972
https://willcoxcorvette.com/corvette...ind-grille-69l
Also do not be fooled ...Your metal vacuum storage tank can have issues with it due to cracks in the metal ...which effects how the system works. If your vacuum system cannot hold vacuum...then you can have problems.
https://www.corvetteforum.com/forums...nk-repair.html
DUB
https://willcoxcorvette.com/corvette...ind-grille-69l
Also do not be fooled ...Your metal vacuum storage tank can have issues with it due to cracks in the metal ...which effects how the system works. If your vacuum system cannot hold vacuum...then you can have problems.
https://www.corvetteforum.com/forums...nk-repair.html
DUB