burnt olds said:
powersrodsmike , you never had one fail , well don't hit them brakes twice .
that vacuum will let you down , and if your running a bigger cam , even that booster can on the fender well want help .
the front port is to mix with them gas's from the engines pcv valve for better burn i read from gm .
that quadrajet should have a port , plugged maybe ?
or it's a older type or made for pontiac or a olds .
some the older chevy's hooked directly in the intake back of carb location .
Why do you feel the need to confuse this issue with scenarios that do not exist..
The OP has said nothing about having a "big cam",or low vacuum, and as far as we know he only has one port on his carb.
If he only has one port, like most Holleys do, then using a T to get vacuum to his brake booster will present no problems.
You are right about the gases mixing better when they go into the front of the carb, but as the function of the booster will not change the function of the PVC system enough to make any difference.
burnts olds said:
powersrodsmike , you never had one fail , well don't hit them brakes twice .
You act as if I am guessing about this, I am not guessing, I have plumbed many cars with a T into the PVC line, even cars equipped with a blowers with no problems. (blown cars make alot of vacuum at the baseplate of the carb, as long as the carb is on top of the blower
) My own Blazer, with a moderate cam, has had a T'd line running to the PVC and booster for over 100000 miles with no loss in brakes, even when towing a loaded car trailer, and the motor is doing fine.
If what you "read", differs from my experience, then that does not make my experience wrong.
Many holleys come with 1 big vacuum port, used quite regularly to serve both the PVC and brake booster.
The ability for a running motor to create a vacuum through any port in the manifold is the same, as long as the channels from the port are ported to someplace under the throttle plates, and the channels are large enough to flow properly.
A 3/8" port on a carb is is ported to plenty large enough channels.
Beyond the point when the vacuum is drawn down in the booster, it requires no constant source of vacuum, as long as the diaphram is intact and the check valve is functioning properly. This allows the pvc valve to function as it should .The only time that booster needs to have an
increased flow of vacuum is when it is activated. Typically when the booster is activated, the throttle plates are closed, the motor is decelerating and the vacuum is the highest, and the need for the pvc valve to allow crankcase gases to enter the intake are the lowest..
If, as you have speculated,
that vacuum will let you down
,then the OEMs would not have designed millions of cars with a vacuum booster to assist in braking.
If a long cam/low engine vacuum or so much blowby that the pvc valve is overwhelmed is a problem, that is a whole seperate issue, and no matter where the vacuum gets hooked to on the carb or manifold it won't let the booster work properly.
If the OP plumbed a vacuum line into the manifold with a supercharged motor, he'd really be asking for trouble.
( I was amiss when I asked if he had a port on the manifold, my initial reading of his post missed the fact that he has a blower. My mistake. )
If you understand the way those systems work, instead of trying to keep everything hooked up the way the factory did it, you would understand that there is no problem..
Later, mikey.