i have a '68 with a 427 big block. I have been running ethanol free 93 octane fuel thru it with no serious issues but a little smoke. Yesterday I filled tank with ethanol free 110 octane ( original owner recommended this) It ran fine but this morning I started her up and the headlights came up on there own! I tried to use switch and the manual override but no effect. I am assuming that the difference in fuel may have somehow changed pressure in the air lines? I dont know how this happened but they are staying open and I want to figure out how to get them closed and fixing the issue to keep it from happening.

 

Little Blue Pill comes to mind.
"If your headlights stay up for more than 4 hours after taking 110 lead racing fuel, seek medical attention immediately".

Seriously, I don't see a connection.
Headlights run on the vacuum pressure of the engine, and I don't think higher octane is capable of affecting the vacuum pressure - it's mostly a function of the cam shaft profile (?).

 

I do not get the joke with seeking medical attention or if that is a joke for this here corvette rookie.
That's cool if the fuel has nothing to do with it. It's the only thing different I did to car , other than that it was just a random thing with the lights going up on their own. any idea how to fix that?

 

Sorry - my poor attempt at middle-aged male humor (you may be the in the minority of not fitting into that demographic for this board!)
The "joke", was that your car must have REALLY liked the hot fuel.

I too like to top off with 110 racing fuel on occasion, but mainly as a "treat".
At ~$7.50/gal here in Michigan, I use it only to supplement the 90 rec fuel (0% ethanol) that is available around me - maybe 5 gallons or less to top off every 2nd or 3rd tank fill-up or so.

 

Blue pill=viagra / headlights going UP.... Actually it was funny but I'm an immature 56 yo.

On a 68 they have only one headlight relay in the center of the nose between the horns. Most likely it had sprung a leak (very common) or the hose has come off the control vacuum on the top of the actuator relay(black hose) or up at the light switch or the over ride. The reason they open is the valve is spring loaded, and when you lose vacuum on the valve, it is forced down by spring pressure to the open fail safe position. You can make the headlights go down by switching the blue and red hoses that go to the headlight actuators them selves. But you will need a new actuator if its leaking or find the leak in the hoses. If you have a stethoscope or a length of hose stuck in your ear, you can listen to the valve and if you hear air moving at he bottom of the valve with the motor running, it is bad. Hopefully its not the headlight switch. Its a pain in the *** ( and back) to replace as you have to loosen the dash and climb underneath to replace it or pull the dash off, (not recommended as the wiring harness is a hassle to deal with.)

on the headlight Actuator relay

• the black hose #1 pulls vacuum to make the headlights go up
• the yellow line is the vacuum that does the work up or down
• swap the red and blue lines on the relay to get your headlights to close for a temporary fix so you can go out in the daylight only
• the black hose is where your leak is, at the actuator or all the way up at the over ride or the headlight switch. Or the actuator relay itself. (If its the relay buy 2 because the wiper door relay is the same. Buy them from Willcox so you can make surre you get a quality part. The reproductions are generally poorly made and leak easily or dont last long.)
• If you have a vacuum gauge plug it in at the actuator relay end of the hose with the light switch in the off position and you should have vacuum, if not its the headlight switch, over ride or hose connections between

ACTUATOR

ACTUATOR RELAY