Vacuum required to stroke 68 RS cover - Team Camaro Tech
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post #1 of 10 (permalink) Old Jan 30th, 01, 08:45 AM Thread Starter
Join Date: Feb 1999
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Hello everyone. I'm just about done my 13 year project but my headlight covers are in the way of completion. I have a 68 RS/SS. I purchased all new hosing and actuators & mounting hardware. I rekitted the cover assemblies and they rotate smoothly. I also cleaned up and pressure tested the vacuum can. But my headlight covers will not rotate unless I manly assist them. I have cammed up my 396 a bit but nothing wild. So my question is : What vacuum is required to stroke the covers??? If I get the # and my system does not have enough vacuum then at least I won't have to tear everything apart.
And if I don't have enough vacuum what can I do????
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post #2 of 10 (permalink) Old Jan 30th, 01, 09:01 AM
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i bet you do not have enough vacum. get a vacum pump off a cadalac or some other GM 4 banger auto from a junk yard, wire it to the head light switch, use a relay , i bet you could tap in to the power wire for the head light's a the signal wire for the relay and have the power come right off the bat to the vacum pump.

if memory serv's me they like around 19inch's of vacum and up...hope this help's. also you should be taping the vacum off of a full vac source like from the power brake vacume port on the carb.

most manifold's have a vacum port off the right side only, this is not a full vacum port it get's it from only 4 cylnder's it can make a diferance in volume of vacum and that might also be your problem, and you do have a anit back flow valve in the line before your canister?? if not you will have drop in vacum as you excelerate.

hope this help's! good luck.

[This message has been edited by ilbl8 (edited 01-30-2001).]
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post #3 of 10 (permalink) Old Jan 30th, 01, 09:49 AM
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Are your Actuators orig. GM or Repo ? If Repo are they early Repos? The early Repo's are no good. Just a thought.
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post #4 of 10 (permalink) Old Jan 30th, 01, 12:27 PM Thread Starter
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Thnx for the responses. My original actuators were missing so I bought repos about 1 year ago. So are these old or not, not sure?? Another thing that I forgot to mention, when I take the hose with the vacuum in it off the headlight switch there only seems to be a small amount of "suck" against my finger. That's why I'm wondering what the vacuum should be. My vacuum line is connected to the 3 way tee in the middle of the manifold as original.
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post #5 of 10 (permalink) Old Jan 30th, 01, 01:57 PM
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1 year old actuators are most likely the old stock versions. i had to change mine out 'cause they did'nt work. i puchased new ones about a week ago and they now work. make sure you have the one way check valve in place as well.
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post #6 of 10 (permalink) Old Jan 30th, 01, 04:14 PM
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I don't think the system really requires a large amount of vacuum from your motor. It has a canister (reserve) that should build it and store it. I don't remember if it is the same for the '68 but the '69 hose kit tells you to hook the hoses up wrong. Switch the red and green just below the overide slider that allows the doors to stay open, start the car up and then pull the overide plunger and see if they open.

Of course this could be a combinition of several thing so don't give up... Think of the vacuum flow in the hose just like electricity.

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post #7 of 10 (permalink) Old Jan 30th, 01, 05:31 PM
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Just went thru my 68 RS. New motors and switch. I had problems at first,but found my vacuum lines were reversed on the headlight switch,huum,whats that vacuum sound from the dash? Anyway,it seemed it only took 5 or so inches to make them work.The vacuum that the headlamp switch,switches,only moves the vacuum solenoid. Basically I would check for a vacuum leak,pinch off the main hose at the intake manifold and see if your RPM changes.I'm sure it didn't take any more than 10" of vacuum for them to open.Like the other post, check your vacuum check valve. good luck, Dale

68 z28 68 rs 327 73 454 vette
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post #8 of 10 (permalink) Old Jan 31st, 01, 04:48 AM Thread Starter
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One thing that I may have done wrong is that the instructions that came with the new hosing said to not put the check valve in line on a 68 and only use it on a 69. My original hoses came in a milk crate and the check valve was there. I haven't installed it so that might be my problem. And I have now heard a few people say that the instructions are wrong in relation to the red and green actuator hoses. I have the red hose connected to the front of the actuators and green to the back. Where do they connect on the vacuum canister or does it not make a difference on the can????
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post #9 of 10 (permalink) Old Jan 31st, 01, 06:21 PM
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The vacuum canister is connected to the center port. The front of the actuator (red,on my car) is connected to the lower port. Obviously the rear of the actuator,is connected to the top port.I dont know if my colors are correct,but they work great. I think the hose from the canister to the valve, is yellow? Mine's just 5/16 fuel hose,2 pieces,approx. 5" long, connected by the tee which goes to the headlight switch. Hope this helps.

68 z28 68 rs 327 73 454 vette
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post #10 of 10 (permalink) Old Feb 1st, 01, 09:11 AM
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The reason the can connects to the center part of the vacuum switch is that it supplies constant vacuum and as you turn on the head lights the piston inside moves up using the vacuum from the dash switch. This puts vacuum to the red hose causing the doors to open and the green hose is open to atmosphere to allow air to escape from the back side of the actuator. Closing is the exact opposite. I do have a check valve from the main manifold to the switch and to the can to keep from loosing vacuum, it has one large inlet and one small outlet and one large outlet.

Here is my answer to a past post.


Actually there is no vacuum at the overide switch on the line that comes from the dash switch until the dash switch is turned on. but there is constant vacuum to the canister and through the yellow hose. I know when I bought my hose kit the directions were backwards for the actuator hose connections and I was having the same problem, so I switch the hoses at the actuator and mine work great.

The dash switch only adds vacuum (when pulled out) or takes away vacuum (when pushed in) from the relay switch. If you look at the relay switch when off the car you can see that the small hose connection is used to pull the internal plunger up when vacuum is applied thus allowing the main vacuum which enters via the Yellow hose to the Red hose circuit and the actuators ( in theory) should open.
Now all instructions I have seen show the Red hose connected to the back of the actuators. This is WRONG. Red connects to the front and Green to the back. If in doubt use a hand held vacuum pump and this will show you what I am explaining.

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