where do I get vacum for a brake booster

[andys70c10]

my truck is a 3 spd manual & i'll be doing this soon. the vacum off the bottom of the carb goes to my pcv valve, can i tee off this?

[soba_03]

Andy,

I believe that if you tee off the carb in that location you will only have vacum when the throttle plate is opened which is generally not the case when braking. I believe that port is vaccum advance port. I might be completely wrong here. SO SOMEONE please correct me.

You should be able to tape off of any of the intake spots ported for vacum. You obviously loking for a constant source of vaccum and I don't believe that carb base is your best choice.

Good luck.

[Bus Ted Knuckle]

Factory power brake trucks get vacuum from the rear of the carb base. If your truck never had power brakes and the carb is original, your base is probably not drilled and tapped there. You can drill it and tap it, I did that on my scrap yard truck, or you can put a T on the manifold and go thet it from there.

[Andy4639]

I agree you want a vacuum port that has vacuum the whole time. Never hook it up to the carb.

[cruiserman]

PCV goes to air cleaner spacer on my truck. Booster goes to the back of the carb.

[Sinister]

On my '69 there is a tee that's towards the back of the intake manifold. It feeds the power brakes and the vacuum modulator on the tranny...

[Bus Ted Knuckle]

Originally Posted by Andy4639

I agree you want a vacuum port that has vacuum the whole time. Never hook it up to the carb.

there is just as much vacuum on the bottom of the carb as there is any where else on the manifold, more even. And like I said in my original post, the factory put them to the rear of the carb base

[Longhorn Man]

the confusion here is, on the carb, you have manifold vacume, which is full vac all the time, and you have ported vacume, which is only when you hit the throttle.
The fittings up high are part time ported vac, the lower ones (like where the factory ran the booster hose to) is full manifold vacume.
You can put it on the intake if you like, HOWEVER... You'll want to make sure that the port gets vacume from all the engine, not just on one runner to one cylinder. I had a booster pop on my first caddy engine, and it was ran to one cylinder. The rush of fresh unregulated air to that one cylinder caused an instant lean condition and shattered a piston.

[andys70c10]

I just went out & looked & my vacum line is coming off the base of the carb going to my pcv valve, It has a screwed in fitting if i'm not mistaken its the same place that it was on the truck I took the setup off of. I also have another smaller vacum port next to it that runs to my air cleaner. i have a factory style ugly air cleaner assy. that i'll be taking off soon. could i just run it off that?

[ChevyC102007]

On the Rochester Carb the power brake booster runs to that screwed in port. Your PCV should run to the air cleaner lid into a small filter built into the side of the main body of the cleaner. Then those gasses are pulled down into engine and burnt. (Emmisions deal). someone can correct me on that part but thats the way the booster is set up on the Q-Jet on my truck.

[VDOG]

Originally Posted by ChevyC102007

On the Rochester Carb the power brake booster runs to that screwed in port. Your PCV should run to the air cleaner lid into a small filter built into the side of the main body of the cleaner. Then those gasses are pulled down into engine and burnt. (Emmisions deal). someone can correct me on that part but thats the way the booster is set up on the Q-Jet on my truck.

I have an Edelbrock 1406 and there is nothing on the back of the carb for a booster line. Where do I hook mine up?

[ChevyC102007]

A friend of mine told me that if you change to another carburetor other than the factory Q-Jet, you can hook into the plugged port between the carburetor/ distributor(middle of the intake as viewed from the front between the runners on stock manifold, aftermarket manifolds have it on the edge of #8 runner). Seeing as how the power booster runs off manifold vaccum I think this could work. Otherwise try calling the Edlebrock Tech Line...they may be able to help if ya havent already.) Im sure someone else on the board can correct me on this but its just my $.02

[chevguy7]

Originally Posted by Sinister

On my '69 there is a tee that's towards the back of the intake manifold. It feeds the power brakes and the vacuum modulator on the tranny...

Same here, I just did the conversion for front power disc.

[VDOG]

Originally Posted by chevguy7

Same here, I just did the conversion for front power disc.

Could you post a pic?

[70rs/ss]

On the back of your edelbrock carb (you'll need to unbolt the carb to see it, or stand on your head under the hood ) there will be an allen headed plug screwed into the base of the carb at the rear of the carb. Take the plug out and get a hose barb fitting, thread it in and that is the PB vacuum port.

[VDOG]

Originally Posted by 70rs/ss

On the back of your edelbrock carb (you'll need to unbolt the carb to see it, or stand on your head under the hood ) there will be an allen headed plug screwed into the base of the carb at the rear of the carb. Take the plug out and get a hose barb fitting, thread it in and that is the PB vacuum port.

Stand on my head!! LOL
Ok I felt that plug behind the carb, now it makes sense. A hose barb fiting, is that what its called?

[70rs/ss]

yeah a threaded hose barb, NAPA or any decent parts store.

[VDOG]

Originally Posted by 70rs/ss

yeah a threaded hose barb, NAPA or any decent parts store.

Thanks, on my way!

[chevguy7]

Originally Posted by VDOG

Could you post a pic?

Sure, I will do it tonight.

[chevguy7]

Here is the picture of where I am running my vacuum from for the brake booster. I just ran a T from the original one at the back of the intake manifold that also goes to the transmission. Let me know if you need a different one.