How can I boost vacuum?
Thread Starter
Team Owner
Joined: Aug 2006
Posts: 24,125
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From: Columbia Missouri
How can I boost vacuum?
My 350 is fairly stock. I rebuilt it liek six years ago, but used stock replacement parts. The vacuum system all works...healights, climate control and the like, but sometimes it seems I have to wait for vacuum to build up before I can get the lights up quick.
I know when I build and put in the new 400 I'll have less vacuum than I do now. What are some ways I can boost vacuum in the system? Aren't there little electric vacuum pumps that pull air out aiding the vacuum system? Any thoughts?
I know when I build and put in the new 400 I'll have less vacuum than I do now. What are some ways I can boost vacuum in the system? Aren't there little electric vacuum pumps that pull air out aiding the vacuum system? Any thoughts?
Melting Slicks
Joined: Mar 2006
Posts: 3,342
Likes: 7
From: Connecticut
Originally Posted by Durango_boy
My 350 is fairly stock. I rebuilt it liek six years ago, but used stock replacement parts. The vacuum system all works...healights, climate control and the like, but sometimes it seems I have to wait for vacuum to build up before I can get the lights up quick.
I know when I build and put in the new 400 I'll have less vacuum than I do now. What are some ways I can boost vacuum in the system? Aren't there little electric vacuum pumps that pull air out aiding the vacuum system? Any thoughts?
I know when I build and put in the new 400 I'll have less vacuum than I do now. What are some ways I can boost vacuum in the system? Aren't there little electric vacuum pumps that pull air out aiding the vacuum system? Any thoughts?
Thread Starter
Team Owner
Joined: Aug 2006
Posts: 24,125
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From: Columbia Missouri
Originally Posted by Bob Onit
First of all, what IS your Manifold vacuum.... get back with the number and then you may get some correct answers
You know what? I haven't measured. I'll do that. Umm...what should it be?
Racer
Joined: Apr 2005
Posts: 402
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From: Nassau
You could always go electric. Im going this route with mine when I finally get that far in my rebuild. http://www.mcspeed.homestead.com/Our_Products.html
Former Vendor
Joined: Nov 2005
Posts: 683
Likes: 1
From: Mounds View Minnesota
Anything above 10 inches of Vacuum is enough to operate the headlights and brakes.
If it's slow then you might have a bad or missing checkvalve.
There should be two ( at least ) One that plugs into the brake booster disguised as a 90 degree fitting and the other between the Vacuum can and the intake manifold.
If it's slow then you might have a bad or missing checkvalve.
There should be two ( at least ) One that plugs into the brake booster disguised as a 90 degree fitting and the other between the Vacuum can and the intake manifold.
Thread Starter
Team Owner
Joined: Aug 2006
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From: Columbia Missouri
Originally Posted by Corvette Engineering
Anything above 10 inches of Vacuum is enough to operate the headlights and brakes.
I'll test this, but I don't have a vacuum gauge and will need to borrow or buy one.
How long should it take an engine to achieve 10" of vacuum?
Originally Posted by Corvette Engineering
If it's slow then you might have a bad or missing checkvalve. There should be two ( at least ) One that plugs into the brake booster disguised as a 90 degree fitting and the other between the Vacuum can and the intake manifold.
Could an engine achieve proper vacuum without one of these?
Melting Slicks
Joined: Mar 2006
Posts: 3,342
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From: Connecticut
Originally Posted by Durango_boy
How long should it take an engine to achieve 10" of vacuum?
The vacuum is highest at idle
My stock L-48 reads about 20"
Race Director
Joined: May 2006
Posts: 16,528
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From: Dayton, Ohio
Originally Posted by Durango_boy
I'll test this, but I don't have a vacuum gauge and will need to borrow or buy one.
How long should it take an engine to achieve 10" of vacuum?
Hmm...my Vette doesn't have one of these. I guess good ol' Bubby removed mine back in the '80's before I owned it. Bummer.
Could an engine achieve proper vacuum without one of these?
How long should it take an engine to achieve 10" of vacuum?
Hmm...my Vette doesn't have one of these. I guess good ol' Bubby removed mine back in the '80's before I owned it. Bummer.
Could an engine achieve proper vacuum without one of these?
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Thread Starter
Team Owner
Joined: Aug 2006
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From: Columbia Missouri
Originally Posted by dwncchs
You should have around 15" at idle-you probably just have some leaks or are missing your check valves.
I'm sure I don't have leaks, but I"ll have to check on the check valves. Also, what about the vac can? Needed or not?
Thread Starter
Team Owner
Joined: Aug 2006
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From: Columbia Missouri
Originally Posted by dwncchs
Can? vacumn adv. on distributor?
Someone mentioned the check valve between the vacuum can and the engine. My Vette does not have a vac can, and I wonder if that's why I don't have strong vacuum...or at least I assume I don't without checking with a gauge.
The reason I think it just takes time for my vac to build, or that it isn't very strong...is say I start the Vette at night, and immediately turn on the headlights. They won't pop up immediately, and they come up unevenly. If I let it idle for a few seconds, maybe 15 seconds or so, and then turn on the lights, they both pop up strong and fast.
Thread Starter
Team Owner
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From: Columbia Missouri
Originally Posted by dwncchs
Bob-- wont be 20 after that big ole cam install !!!!!
That's the other reason I ask. I'm building a new motor, and it'll have a larger cam, a ZZ4 cam. I was told it'll have lower vacuum at idle so I started thinking I would need to boost this using an electric pump of some kind.
Race Director
Joined: May 2006
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From: Dayton, Ohio
Originally Posted by Durango_boy
Someone mentioned the check valve between the vacuum can and the engine. My Vette does not have a vac can, and I wonder if that's why I don't have strong vacuum...or at least I assume I don't without checking with a gauge.
The reason I think it just takes time for my vac to build, or that it isn't very strong...is say I start the Vette at night, and immediately turn on the headlights. They won't pop up immediately, and they come up unevenly. If I let it idle for a few seconds, maybe 15 seconds or so, and then turn on the lights, they both pop up strong and fast.
The reason I think it just takes time for my vac to build, or that it isn't very strong...is say I start the Vette at night, and immediately turn on the headlights. They won't pop up immediately, and they come up unevenly. If I let it idle for a few seconds, maybe 15 seconds or so, and then turn on the lights, they both pop up strong and fast.
Thread Starter
Team Owner
Joined: Aug 2006
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From: Columbia Missouri
Originally Posted by dwncchs
15 seconds isnt real bad but it could be the check valve-its a 3port valve behind carb on drivers side --your vac canister is part of your front bumper_sorta-its up front a big cylinder with ports on it
I have that one...I thought he meant the coffee can looking thing that's sometimes under the fender of the driver's side.
Race Director
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From: Dayton, Ohio
Originally Posted by Durango_boy
That's the other reason I ask. I'm building a new motor, and it'll have a larger cam, a ZZ4 cam. I was told it'll have lower vacuum at idle so I started thinking I would need to boost this using an electric pump of some kind.
Race Director
Joined: May 2006
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From: Dayton, Ohio
Originally Posted by Durango_boy
I have that one...I thought he meant the coffee can looking thing that's sometimes under the fender of the driver's side.
Melting Slicks
Joined: Mar 2006
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From: Connecticut
Originally Posted by dwncchs
Bob-- wont be 20 after that big ole cam install !!!!!
Im bummed about the whole thing as its just too confusing to me
Race Director
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From: Dayton, Ohio
Originally Posted by Bob Onit
That whold idea is quickly becoming something that will most likley not happen....
Im bummed about the whole thing as its just too confusing to me
Im bummed about the whole thing as its just too confusing to me