Best vacuum spot for the Brake booster ?

[Steve Cole]

I have an Edelbrock 1407 carb and a Edelbrock RPM Air Gap intake. My center vacuum port (front) is for the PCV, the passenger side smaller port is for distributor vacuum advance, the rear port is for the vacuum modulator on my t400. My valve covers contain the PCV and a breather/oil fill. I am assuming I need to tap directly into the manifold for the booster, but where ? There is a threaded port in the back center area that may work but I don't know for sure.

Can anyone point me in the right direction?
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[LONGHAIR]

Yeah, the intake runner across the back, it will have a larger threaded hole, plugged. Just install a fitting that fits the hose you have.

[mmiddle]

Originally Posted by Steve Cole

There is a threaded port in the back center area that may work but I don't know for sure.

Can anyone point me in the right direction?
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Yep, That what that port is for.

[treveiger]

Hey I needed this info to. Thanks!
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[Steve Cole]

Just so I'm clear, we are talking about this plug directly under the carb nipple right?

[LONGHAIR]

Yup. It's a good idea to run you shop-vac, sucking as close to the fitting as you can while removing it. This is your best shot at keeping any kind of crusty junk from dropping into the hole.

[Steve Cole]

Will do, Thanks Longhair and Mmiddle!

[Murphy IRE]

Just out of curiousity, how many inches of vacuum do you have? Even tapping into that, I didn't have enough for my booster to work. I wound up going with a hydro boost.

[Steve Cole]

I don't know Murphy, it is a non-running truck that I am putting together.

[GASoline71]

If you have a snotty cam, you won't have enough vacuum for power brakes. From the factory, that hole has a fitting in it for the tranny modulator line. There will be full vacuum from that port. So it should run power brakes just fine. But like I mentioned, if you have a large cam with a lot of overlap... you will need to run a vacuum canister.

If your cam is stock, or a warmed over stocker (RV cam), you will be fine on vacuum.

Gary

[Steve Cole]

Originally Posted by GASoline71

If you have a snotty cam, you won't have enough vacuum for power brakes. From the factory, that hole has a fitting in it for the tranny modulator line. There will be full vacuum from that port. So it should run power brakes just fine. But like I mentioned, if you have a large cam with a lot of overlap... you will need to run a vacuum canister.

If your cam is stock, or a warmed over stocker (RV cam), you will be fine on vacuum.

Gary

Thanks Gasoline 71, but now I am confused because Mister B just asked the same question in another post and he was told to use the rear port on the base of the carb for his booster connection. It made sense because the rear port on my carb base has a large nipple on it similar to the size of the barb on the booster and also what you said about that port in the intake being for the tranny modulator. It seems like you would get full vacuum from the carb base as well wouldn't you? My plan is to use the port in the back of the intake for the tranny modulator and the port on the rear base of the carb for the booster. Can we get a consensus on this from everybody?
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[GASoline71]

The carb port is where it came out from the factory and went to the booster. I would use that one if it were me. I was just saying that you can use the port in the manifold if you want. Just wasn't set up that way from the factory. The factory modulator line went into a small port off the intake.

I'm also not a big fan of using "T" fittings for major vacuum lines like Power Brake Boosters, and Trans Modulators.

Gary

[swamp rat]

If its below the butterfly's on the carb its manifold vacuum, so yes the back port is fine. The plug located on the manifold is also fine..

Rule: if the port is between the carb butterfly's and the valves its manafold vaccum.