Started trouble shooting my headlights tonight. Both came up with minimal vacuum, however they wouldn't go down....
As I drove the car back into the garage, the pass side dropped back down, the driver didnt...

Three questions....

1) can I pull vacuum from a port on the carb (edelbrock on a 454)
2) has anyone pulled from the intake, from the fitting right behind the carb? How did you plumb it, with what fittings?
3) What would cause the winking eye?

 

My new old 1977 has a Right Wink Eye almost every time I start it up after a few days. It is a leak in the pressure lines I believe. It stops winking after a few minutes. Since I have only own my 1977 for a few weeks I think it is the manifold that controls both head lights. I can pull the little bleeder under the dash and it does not help. But it does close after my choke closes and the engine resumes normal idle speed.

I still need to adjust my choke idle speed because it is too high running over 1500 RPMs and it should not be this high. Choke Idle should be about 1000 rpms till the engine warms. I had to adjust the normal idle last weekend because when I bought the car it was running about 1100 RPMs.

I do believe the winking problem on my car is due to too high of a Choke Idle speed.

Winking is caused by vacuum leaks in the parts that close the vacuum. I do not know yet what these parts are yet since I am still exploring a car I have only owned for a short time.

It has been 25 Plus years since I adjusted a Carb and it is slowly coming back to me. Good news I bought all the tools 25 years ago to play with these engines and carbs than never sold the tools.

 

Ive also assumed it was some small leak. Like you, Im also re-learning a new system. The vac coming off the carb just doesnt seem to be enough, but I cant seem to find a fitting that goes from 3/8 NPT to itty vac line....

The system itself seems simple enough, I have a great routing diagram from Wilcox Im using. Its just so dam hard to replicate operating vacuum. Hand pumps and A/C evacuators just dont seem to cut it. If I could find a good vac source, I could readily test the system.

 

You don't need to.

All C3s use the manifold fitting for the vacuum source. Purchase the assembly instruction manual and take a look at the stock set up.

Relay, first. Actuator, second.

 

Mike, do you have some vested interest in the factory assembly manual? I dont think there has a been a question poised yet that you havnt managed to sneak in a shameless plug for the AIM. 8-P
Honestly, my car is a Frankenstein hybrid of an 72 and a 82 and Im not buying 2 different manuals. But, just for conversation, how much do these manuals cost? Maybe I can buy an electronic version for cheaper?
(Thanks for the input, and please realize Im just busting your chops when I ask if you are invested in the manuals. No offense intended. )

 

All C3's have a lot in common so having any AIM is better than none. Every C3 I've seen pulls the vacuum straight from the intake manifold. From there it splits off in several directions. All you really need to trouble shoot vacuum issues is some vise grips and Mite-vac.

 

What does the fitting on the intake look like? My only source (aftermarket intake) is the threaded port just behind the carb. I cant seem to find any kind of fitting to retro fit it with.

 

It looks like a short pipe threaded into the top of the manifold with several hoses connected to it. Mine sits behind the carb. I think the power brake hose connects there too.

 

My lights go down perfect and if I have them up and pull the lol under the dash they stay up with the lights off. Even if I leave the car off a few days come out start it up they still stay up so long as the lock under the dash is pulled. How ever they will not even attempt to go up on their own. I have not tried to fix it yet b/c I don't mind pushing them up from the bottom an eventually I want to put a electric kit on her.

 

When I first got my 74 I had issues with the headlights, one would open then a minute, or two later the other one would open. Same when they closed. I bought a vacuum line kit and replaced all the vacuum lines, it helped as I found some were dried and cracked. I changed both canisters and after that they worked perfect. Go up together and both close together.
My issue was a combination of cracked vacuum lines and leaky canisters.

 

Here is a pic of mine, behind the carb on the passenger side. One outlet goes to the transmission and the other goes to the white vacuum filter.

 

Yeah, thats the fitting I need, and all I can find are 3/8th hose barbs at the local parts stores. Im thinking Im going to need to hit a junk yard or a dealer. Once I get everything hooked up correctly, Ill be able to further diagnose. Ive a feeling that the small vac line from the base of the carb may not be giving sufficient suction.

 

One of these should work for your application: http://www.ecklerscorvette.com/catal...vacuum&x=0&y=0

Steve

 

My drive side pops up if i get on the gas. Not going to fix it because it a great reminder that i neef to take my iver size lead foot off the gas.

 

Nope. All I'm saying is the AIM shows the complete vacuum system, the correct hose routing, the correct hose color codes, and the GM part number for the manifold fitting you're looking for. You can use the diagrams in the AIM to correct most problems with the vacuum system.

With the exception of the wiper door, the 82 vacuum system is pretty much the same as the 72.

Less than $25. Check the vendors for prices.

You can get them on CD.

None taken.