Vacuum-Related
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Joined: Dec 2007
Posts: 58
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From: Austin TX
Vacuum-Related
I spent a few months slowly working through all of the issues with the vacuum-actuated bits of the '71 Vette (thanks to those of you who helped!).
I now have control of all of the moving parts, and can get them to go up and down when the should. Well, almost.
The car doesn't develop enough vacuum until after the choke is off. So when i first fire it up cold, a gauge mounted right after the check valve shows only 5 or so. Once the engine gets warmed up, and starts to run, and you goose the throttle to get the idle to settle down, then the vacuum creeps up to 15 or so in about 20-30 seconds, and everything works great from there. When you turn the vehicle off, vacuum loss is slow. e.g. you can wait ten seconds after you turn the car off, and then turn the headlights on or off and the canister has enough vacuum left to comply, so i don't think i have a massive leak anywhere from the check valve on.
The carb is a Holley, but i don't know the model. It has electric choke. Vacuum lines off the carb include Brake booster, both valve covers, and distributor. Possibly of note there is what appears to be a vacuum port immediately next to the choke, it has a cap on it.
Any ideas?
Thanks!
Paul
I now have control of all of the moving parts, and can get them to go up and down when the should. Well, almost.
The car doesn't develop enough vacuum until after the choke is off. So when i first fire it up cold, a gauge mounted right after the check valve shows only 5 or so. Once the engine gets warmed up, and starts to run, and you goose the throttle to get the idle to settle down, then the vacuum creeps up to 15 or so in about 20-30 seconds, and everything works great from there. When you turn the vehicle off, vacuum loss is slow. e.g. you can wait ten seconds after you turn the car off, and then turn the headlights on or off and the canister has enough vacuum left to comply, so i don't think i have a massive leak anywhere from the check valve on.
The carb is a Holley, but i don't know the model. It has electric choke. Vacuum lines off the carb include Brake booster, both valve covers, and distributor. Possibly of note there is what appears to be a vacuum port immediately next to the choke, it has a cap on it.
Any ideas?
Thanks!
Paul
Last edited by 1FastHaole; Mar 8, 2010 at 07:49 AM.
Race Director
Joined: May 2006
Posts: 16,528
Likes: 53
From: Dayton, Ohio
You have a leak in your system, tank,lines,valves etc. Now all you have to do is isolate ,which because you have a vac gauge in line should be easy. Just start pinching off hoses going to things like the tank , head lights , brake booster while watching the vac gauge. When you see a rise , follow the hose to the leak. It helps sometimes to have multiple pinchers so you can pinch more than 1 hose at a time.
