Adding Power Brakes - Vacuum Question

[redwards69]

Is it better to use vacuum port on intake or back of carb, or does it matter? PCV is attached to front of carb as it should be.

 

[jckkys]

The factory used a vacuum tree behind the carburetor. It splits to both levels of the 2 plain intake. The front PVC port was only used on the '76-'77s but in makes a more sanitary plumbing arrangement for the PVC and breather.

 

[redwards69]

The factory used a vacuum tree behind the carburetor. It splits to both levels of the 2 plain intake. The front PVC port was only used on the '76-'77s but in makes a more sanitary plumbing arrangement for the PVC and breather.

Thanks. I probably should have noted nothing is stock, but I guess it doesn't matter. It's a 302 with an Edelbrock Performer 2121 intake and an Edelbrock 650 carb.

 

[jckkys]

On a Performer the vacuum tree would go in the hole on the top of the cylinder #4 runner. The PVC port is in the front of the AFB as you said.

 

[DirtDonk]

While the typical install for the booster is from the intake, either through a single cylinder runner or a common area, it should not matter if you want to hook it up to the base of the carb. I've never used a carb fitting for a brake booster, but as far as I can tell, as long as it's full flow and not regulated by any restrictions, either location would be fine.

Paul

 

[redwards69]

Thanks guys. I'll mount via the manifold.

 

[stlo]

Mine is on the manifold as well

 

[gr8scott]

I run mine off a vacuum tree on the back of the carb. That yellow hose (pcv) has been relocated to the
front of the carb. She was robbing too much vacuum from my booster.

 

[Broncobowsher]

The PCV is a continuous flow. You want that at the base of the carb to evenly distribute the vapors to all the cylinders.

Brakes is just a momentary demand. Going to a single cylinder will be just fine. You might be able to pull just a hair more vacuum off a single intake runner as the vacuum pulses can peak higher than at the common plenum area. So over the course of a few revolutions of the engine the vacuum (via the check valve) may build up a little higher that way. That one cylinder may run just a hair lean for a couple of revolutions, but you will never notice.

 

[redwards69]

The PCV is a continuous flow. You want that at the base of the carb to evenly distribute the vapors to all the cylinders.

Brakes is just a momentary demand. Going to a single cylinder will be just fine. You might be able to pull just a hair more vacuum off a single intake runner as the vacuum pulses can peak higher than at the common plenum area. So over the course of a few revolutions of the engine the vacuum (via the check valve) may build up a little higher that way. That one cylinder may run just a hair lean for a couple of revolutions, but you will never notice.

Thanks. Anyone have a link to a fitting that will fit my manifold (Edelbrock 2121)?