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  #1  
Old Mar 10th, 10, 10:06 AM
OstOgBajer OstOgBajer is offline
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Brian
 
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Default Brake Booster and Carb Vacuum

I have a Holley 650 or 670 (somewhere around there) and the previous owner jammed a screw into the power brake vacuum port on the carburetor because it didn't have power brakes. I'm upgrading to power brakes right now and need now need to use the vacuum port on the carb. Because the PO jammed a screw in there, I can only assume that a vacuum hose nipple won't press nicely into place into that port anymore. Anyone have any advice on what to do? And where do I get the nipple that fits into the port so I can attach a vacuum line?
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  #2  
Old Mar 10th, 10, 12:09 PM
need2speed need2speed is offline

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Default Re: Brake Booster and Carb Vacuum

You should have a 3/8" vaccuum port on the rear of the carb under the real fuel bowl for the power brakes. That would be a large opening to plug with a screw. In the event you can not connect to this port, you have two other choices.
1. See if your intake manifold is drilled and tapped in the back. You can removed the plug and screw in a 90 degree vacuum port. You can connect your brake booster hose to it.
2. Buy a small aftermarket carb spacer (1/2") with a ported vacuum port. You can install it between your carb and manifold (you'll need a carb gasket on either side of the spacer). This will give you adequate vaccuum for the booster, but you may need to tweek your carb setup due to adding the spacer.

Good luck.
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  #3  
Old Mar 10th, 10, 11:26 PM
Garfields Maro Garfields Maro is offline
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Garth
 
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Default Re: Brake Booster and Carb Vacuum

Yep, should be a tapped hole in the manifold for the brake booster. The one on the carb is generally used for PCV. I gotta wonder how well a "jammed screw" seals/plugs the vacuum port ? May be a slight vac. leak ?

Not sure what to tell ya as far as repairing the POs "screw" up. I'd say try screwing it out and see....If too buggered up, may need to remove carb and carefully dress it out with a file to remove burs. I think a 3/8" OD piece of thin wall tubing and a skim coat of Permatex would work....then plug it with a vacuum cap or hook up a PCV Probably could find the correct nimple too, but I'm not sure where ?

....or, if you're afraid of it and not using a PCV, leave it be and smear some goo-pucky around the screw to be sure it doesn't leak
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  #4  
Old Mar 11th, 10, 05:00 PM
OstOgBajer OstOgBajer is offline
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Brian
 
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Default Re: Brake Booster and Carb Vacuum

Could I just put a "T" fitting in the PCV line and send that to the booster?
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  #5  
Old Mar 11th, 10, 05:27 PM
daves80z28 daves80z28 is offline
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Default Re: Brake Booster and Carb Vacuum

Quote:
Originally Posted by OstOgBajer View Post
I have a Holley 650 or 670 (somewhere around there) and the previous owner jammed a screw into the power brake vacuum port on the carburetor because it didn't have power brakes. I'm upgrading to power brakes right now and need now need to use the vacuum port on the carb. Because the PO jammed a screw in there, I can only assume that a vacuum hose nipple won't press nicely into place into that port anymore. Anyone have any advice on what to do? And where do I get the nipple that fits into the port so I can attach a vacuum line?
the brake booster needs manifold vacuum...should be a threaded hole on the intake to mount a vacuum port, then put booster line to that
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  #6  
Old Mar 11th, 10, 10:21 PM
Garfields Maro Garfields Maro is offline
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Garth
 
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Default Re: Brake Booster and Carb Vacuum

Quote:
Originally Posted by OstOgBajer View Post
Could I just put a "T" fitting in the PCV line and send that to the booster?
Not that I recommend it , but apparently some folks have done it this way. Try a search for some different points of view...here's one...http://www.camaros.net/forums/showth...vacuum+booster

So, are you saying ya can't find a vacuum port/provision on your intake manifold
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  #7  
Old Mar 11th, 10, 10:29 PM
OstOgBajer OstOgBajer is offline
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Brian
 
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Default Re: Brake Booster and Carb Vacuum

I just went out and took a look and I found a provision on the intake for manifold vacuum.
Just need to get a 90 degree fitting. Thanks for the help!
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  #8  
Old Mar 11th, 10, 11:28 PM
jcrich54 jcrich54 is offline
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Jim
 
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Default Re: Brake Booster and Carb Vacuum

I don't mean to jump in on this but I have just about the same problem where to hook up my power booster I have a Ebelbrock Victor JR manifold on my 383 stroker and there is no manifold vacuum ports on it and my PVC valve is hooked up to the base in the rear of my carb which is a Holly 670 CFM carburator, I do have another port in the front of my carb at the base, can I pull vacuum from it to hook the PVC or the power booster up to, Thanks

Last edited by jcrich54; Mar 11th, 10 at 11:52 PM.
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  #9  
Old Mar 12th, 10, 01:03 AM
Steiner Steiner is offline
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Default Re: Brake Booster and Carb Vacuum

Quote:
Originally Posted by jcrich54 View Post
I don't mean to jump in on this but I have just about the same problem where to hook up my power booster I have a Ebelbrock Victor JR manifold on my 383 stroker and there is no manifold vacuum ports on it and my PVC valve is hooked up to the base in the rear of my carb which is a Holly 670 CFM carburator, I do have another port in the front of my carb at the base, can I pull vacuum from it to hook the PVC or the power booster up to, Thanks
If it is a 670 Street Avenger, the 3/8" port on the rear side is designated as the brake booster port and the 3/8" port on the front corner is designated as the PCV port. There is also a small full manifold vacuum port on the front corner that is good for connecting an in-car vacuum gauge or for using while tuning. The one on the side above the throttle plates is ported vacuum for if you want to run ported vacuum spark advance.
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  #10  
Old Mar 12th, 10, 02:21 AM
jcrich54 jcrich54 is offline
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Default Re: Brake Booster and Carb Vacuum

Thank's Steiner, so the small vacuum port up front I can use for my Vintage Air vacuum ?, and that solves that porblem, now I just need to get the right exhaust set up and get my headers on, an March system on, and I will be just about there
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  #11  
Old Mar 12th, 10, 04:45 PM
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scblucam scblucam is offline
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Default Re: Brake Booster and Carb Vacuum

jcrich54 the Victor Jr rpm range is 3500 to 8500, most engines that run in that range don't have much idle vacume.
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  #12  
Old Mar 12th, 10, 07:13 PM
Steptoe Steptoe is online now
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Steps
 
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Default Re: Brake Booster and Carb Vacuum

Quote:
jcrich54 the Victor Jr rpm range is 3500 to 8500, most engines that run in that range don't have much idle vacume.
And in the real practical world it doesnt matter
Check out older posts explaining why
Been there done that.
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