Question: headlight vacuum

[redvet1978]

how much vacuum is needed to open and close the headlights on a 1978 corvette? do they need their own vacuum source from the big fitting in rear of intake or can they be ran off a small port on carburater? also where can i find a fitting for the intake? i believe it is a 3/8" npt
will a single hose barb on the fitting work or will i need a double one? it looks like there are 2 vacuum lines that run to it.

 

[petes74ttop]

Vacuum problems.

A stock motor will produce about 18'" of vacuum, if you have a big cam you'll produce less. If you have an automatic transmission the fitting on the manifold will have 2 ports, one for the transmission and one vacuum system. Leave the port on the carb going to the power brake booster alone. All the vendors have fittings to suit your motor and transmission combination, what do you have? Stick or auto?. PG.

 

[raybies]

The headlight vacuum feed on my 1980 is directly off the tree at the back of the manifold and the same line feeds the body connector to the heater controls. There is a 3 way vacuum delay valve in that line also.
Vacuum headlights Ha love to meet the genius who came up with that concept.
Good luck
Ray

 

[redvet1978]

thanks for the info...i have a 4 speed tranny. the stock intake had a 2 port fitting on the back of it. one went to the headlights and i am not sure where the other went. i recently pulled the motor and when i put it back in i had a vacuum line nightmare. unfortunately i did not lable them. i have purchased all new headlight vacuum lines and hooked it all up according to the line diagram. i teed off the other line off the intake fitting and hooked into all other lines. it looks like the other line might go to the vapor canister???? if that doesnt sound right can you tell me if i need a second vacuum line or can i just use a single fitting to the headlights and somehow eliminate the other hoses? also do i need that vapor canister?

 

[TJay]

redvette78,

I hope it's ok with CAC to post this link, if not I'm sorry just trying to help. Have a look at this link, it might help you, on the left of the page, look for 'vacuum trouble"

1975 Corvette Convertible

 

[redvet1978]

thanks tjay...that helps a little. the only other dilemma i have is that on mine for some reason i have a second line that came off the intake and not sure where the H@#% it went.

 

[TJay]

thanks tjay...that helps a little. the only other dilemma i have is that on mine for some reason i have a second line that came off the intake and not sure where the H@#% it went.

I can check my 79 vette and see where it might go, if it's at all the same as 78.

 

[redvet1978]

thanks again tjay...i just think i have more lines than i need...geesh!

 

[petes74ttop]

redvet1978, on my car the vapor canistor "T"s into the PCV line.
TJay, that link is great all the information in the text is correct but the connection at the headlight and pull down switch is wrong. PG.

 

[redvet1978]

ok...i installed the new vacuum line kit for my headlights from dash to lights...looks good and lights open and close perfect! i ended up using a hose barb fitting off the intake. i also added the new filter and control valve. my only problem i have now are the lines that come off the vapor canister. there are 3... a small one and 2 medium ones that T to each other and a short piece coming off that. where do these 2 lines go?

 

[73shark]

The vapor (charcoal) cannister has a line from from the gas tank, one from the carb, and one from the manifold. At least that's the way on the '73.

 

[redvet1978]

thanks shark...i will try that and see if it works out.