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Probable slamming the gate after the horse has bolted. The 383 I have in my 1977 only produces 10" approximately of vacuum at idle. If I decelerate, it will peak at around 15" of vacuum. The brakes are surprisingly good, but the heater valves (vintage air), and the headlights do not operate reliably at this low a level. So, I bit the bullet and purchased a vacuum pump kit which will hopefully alleviate some of these problems. Has anyone else tried this. I did look at the electric replacements, but wow, the manufacturers are really proud of them. The pump kit has a vacuum switch to shut it down when a certain level is reached and will turn it back on if the vacuum drops. I have new actuators and vacuum switches, but I know these headlight systems leak from new. I am just a little worried that the pump may run too much and overheat. The unit is very large and heavy, once I have decided where to put it, I will install it to test and let you know. Just asking to see if anyone has any tips, other than a milder cam. This is the unit:
I have 10" of vacuum and mine work fine.....the key is to make sure the system is sealed......check every connection, can and relay...then check them again.....there are like 40 potential leak points in this system.....when it leaks, you will not get the proper "pull"........
Go to: http://www.corvette-101.com/vacuum.htm
Check your system using this guide....
I hate vacuum pumps.....they are noisy and don't last.
I agree, mine runs 11 1/2 inches. blew a headlight actuator rod seal. Vacuum dropped to 5 inches in the line. rebuilt both my headlight actuators and replaced all my vacuum lines. everything's working fine.
2020 Corvette of the Year Finalist (performance mods)
2019 C3 of Year Winner (performance mods)
2016 C3 of Year Finalist
I added a Hella vacuum pump and a handfull of one way valves and Tees. The key is the shutoff pressure sensor. As the other guys have suggested, you can pull a vacuum on your system and use a stethoscope to check all the connections for leaks. The replacement relay valves will just fail. I think I have one that just failed, its about a year old so thats about right for this repop garbage.
Anyway you can trim off a half inch to an inch of your vacuum lines to make sure they get a great seal. Then you will have to add in the one way valves and Tees so that when your Vacuum Pump kicks on its isnt trying to vacum out your manifold. I added them in and seperated the systems so that it takes a vacuuum on the main system and the tank and put one in so that when the VP shuts off it isnt a source of a leak. I'll try and get a diagram togther
Thank you Rescue, and everyone who answered. I was going to keep a check valve from the manifold, then add the pump after that, and add a check valve before the reservoir so hopefully it wont bleed down. I do have new vacuum switches, and actuators and hoses. Running with a vacuum pump, the headlights pop open and closed. Without it, I can get them to open while slowing down (high engine vacuum), but without doing that, the are very lazy. They behave exactly the same as they did with original valves and actuators. The headlight buckets have been rebuilt and operate very smoothly with the over center locks etc working perfectly. All of the fittings are tight with teflon tape and the hoses are all tight fits. I have small fuel line clamps and have even considered using those on the metal fittings on the tank, which doesn't have a leak. The problem with the vacuum pump is that is is quite big and heavy. With the Fuel injection, the relay panel for the fans and pumps, etc, there is not a lot of room left for it.
I ran a new larger diameter line from the vacuum line for the brake booster to the headlight check valve. They open and close now, but still take a good 5-10 seconds to complete the cycle. I believe the problem is actually in the switch and is causing the vacuum relays to actuate and release slowly thus affecting the headlights. So, I will check this next. Tested the system using an A/C purge pump and they open and close nicely.
Low Vacuum and headlights
