I have a big block with a Holley 4150HP carb and an 11" booster. I have only one vacuum source on the intake. The "racing carb" has no ports & I have no room for a spacer with a port.

I know many people that run a tee for the PCV & brake booster... Is this O.K., or is there (as a mechanic told me) a chance the booster could suck in oil? How could oil get into the booster, wouldn't the vacuum be sucking the air from the booster as well?

I am trying to avoid yanking the intake & drilling another vacuum port, but not if it's going to kill the booster.

I have a big block with a Holley 4150HP carb and an 11" booster. I have only one vacuum source on the intake. The "racing carb" has no ports & I have no room for a spacer with a port.

I know many people that run a tee for the PCV & brake booster... Is this O.K., or is there (as a mechanic told me) a chance the booster could suck in oil? How could oil get into the booster, wouldn't the vacuum be sucking the air from the booster as well?

I am trying to avoid yanking the intake & drilling another vacuum port, but not if it's going to kill the booster.

Teeing off the pcv valve and brake booster is not recommended but can be made to work in tandem.The pcv valve is a controlled vacuum leak and will delay vac source thru the booster check valve depending on engine rpm and manifold vacuum #,s.
Adding a vacuum reservoir/tank with a secondary check valve will assist your booster..but the available Hg will only be as good as introduced.This normally is not an issue after your 1st decel when manifold vacuum is at its greatest and trapped by the check valves.
The problem lies when you start up with low manifold vac with a healthy camshaft and never generate sufficient Hg.
No need to worry about oil contamination in the brake booster..unless the pcv valve fails open at wide open throttle and the fresh air side is unable to keep up with blowby.At worst..this could lead to check valve failure at the booster from contamination..highly doubtfull though..it would have to be the perfect storm imo.

The Help! section at most auto stores has a filter that you can put in line with the brake booster. It keeps the combustion gases from contaminating the booster.

yeah its called a brake booster check valve.
I have mine Teed off the PCV and no problems whatsoever.

I agree with George, I wouldn't "T" the PVC & brakes. I would do as GM did and drill & tap the intake plenum for a fitting solely for the booster and add a vacuum tank as suggested.

Thanks for all the help guys, this site site is great. I think I will add the T and filter for the short term and plan on tapping the intake long term.

Adding a vacuum booster tank might not be a bad idea either - I make enough vacuum, but the semi-radical cam means stalling isn't out of the question...

Anybody using or suggesting a vacuum pump for the brakes instead? Are these still connected to the engine vacuum, or are they completely self sufficient?

yeah its called a brake booster check valve.
I have mine Teed off the PCV and no problems whatsoever.


I've got a check valve but also the booster vapor filter. You can see it coming off the rear port of the carb.


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