I just installed a 700 cfm holley DP on my engine, but I didn't know where I can get vacuum for my power brakes and HVAC controls. Can I just tee into the pcv vacuum source and just use that, or am I supposed to use the little port on the front of the carb? (it looks way too small to provide the vacuum for the brakes, and it was listed for other vacuum things anyway) I need any advice that I can get. Should I just eliminate the pcv valve and run it to the brakes? I tried that and it worked, but the engine ran like crap when I did it. Again, any advice would be great.

 

Check your manifold for a vacuum port.

 

On the actual intake manifold? I'll check when I get back home (I am up at my dorm right now, but I head home on the weekends). The intake I have on it right now is a holley street dominator. Should that still have a port on it?

 

It should. Behind the carb.

An alternative is a carb spacer with a port in it.

 

The port on the manifold will probably have a pipe plug in it. Pull that out and replace it with a hose barb.

 

thanks for the help guys, I'l try all of that when I get back home.

 

Like this..... works fine...

 

I'd do anything to avoid putting a T in the brake booster line.

 

the T works fine. manifold vacuum is manifold vacuum.

the amount of vacuum available at the T is the same as any where on the manifold or carb base. it works just fine like that.

 

well, I'll check for the port in the manifold, but the tee in the line was something I was already thinking of, I just didn't know if it would hurt anything if I did it (like if the brake booster was going to suck up something from it or something, and I already have a tee in it for the HVAC vacuum. I guess the guy who had the car before me set it up like that. I doesn't even have one of those vacuum canisters hooked up. Would that be important?)

 

Having a static vacuum accessory connected to the T would be acceptable, but not the PCV. The flow through the PCV will reduce the vacuum available to the brake booster. Some people have had problems with this, some haven't. I'd do it correctly and not take the chance.

 

Your concerns are not based on fact, only conjecture.

Manifold vacuum is a lot like like water pressure in a water system. it is uniform throu the whole system. I've had it hooked up like that on my car for years with different motors and manifolds. Not a problem. The brakes work fine. Even with big cams. The amount of airflow thru the PCv is fixed by the orifice in the PCV valve. This small "airleak"
only lowers the vacuum level a small amount and is uniform throu out the system. The orifice in the PCV valve is much smaller than the orifice in the booter's check valve and mega smaller than the diameter of the 3/8" feed hose. Again, the amount of vacuum available to the booster is the same wether the pcv is "T"ed into the same source hose or another hose.
There is plenty of vacuum amount and volume to run the power brake booster.

The response of the boosters diaphram is not different.

The brake booster will no "suck up" anything. Any air flow moves toward the motor.

If your car has a bad brake booster, thats a different issue but the connection point of the lil PCV valve will not effect the booster's performance. It's not an issue.

 

My concerns are based on the experiences of others. I've always connected the PCV and booster properly myself, given that there's little difference in effort either way.

 

I did a plate with a port. Trans-Dapt makes it I think.

 

how big of a plate is it? ( I am going to run into hood clearence issues if I am not careful )