Can I tee my 3/8" PCV line to the brake booster?

Discussion in 'Engine Topic' started by BondoSpecial, Sep 28, 2009.

  1. BondoSpecial

    BondoSpecial Veteran Member Lifetime Gold Member

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    I just swapped the 750 Edelbrock off my 350 to test a 600 Holley DP. The Edelbrock had front and rear 3/8" full manifold ports so I could hook the front to the PCV and the rear to the brake booster. The Holley 4150 600 DP only has one (rear) 3/8" manifold vacuum port. There are no available manifold vacuum sources on my Edelbrock perf RPM manifold - the 4150 holley covers the only NPT manifold vac tap on the manifold and even a carb spacer, which I can't run anyway due to clearance, would not uncover the port.

    My only option is to tee the 3/8" manifold vac line to the booster and PCV. Will this provide sufficient flow to both the PCV and the booster, feeding them from a single line of the same size?

    Just this fiasco makes me want to put the Edelbrock back on
     
  2. 1980RS

    1980RS Veteran Member

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    Don't see whay not, I used to do that all the time never had any problems.
     
  3. theflash

    theflash Veteran Member Lifetime Gold Member

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    You should have one port on the intake itself
     
  4. BondoSpecial

    BondoSpecial Veteran Member Lifetime Gold Member

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    see above, the intake port is covered by the carb, there is no way to get to it.
     
  5. cmonson

    cmonson Veteran Member Gold Member

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    your other option is to tap a hole into the intake. Very easy to do on Aluminum. I would do it with the intake off the car though to avoid metal shavings going into the intake ports.

    I am not sure about tapping off the PVC line. your vacumn amounts going to your brakes will be reduced as you will have a vacumn leak going to the PVC.

    Without a large cam it may work though...
     
  6. BondoSpecial

    BondoSpecial Veteran Member Lifetime Gold Member

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    Yeah i thought about tapping the back of the intake, I'd hate to take it off though and I won't do it on an assembled engine.

    I would only think the booster would have an issue if the 3/8" line was already tapped out on flow but I have no way of knowing this.

    Damn 4150 and edelbrock intake combo - almost like they planned it this way so putting a holley on it caused this problem.
     
  7. FatnLow

    FatnLow Veteran Member Lifetime Gold Member

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    I used a 90 degree fitting on the intake port to gain clearance. If you use the t make sure you check the line from time to time to make sure oil isn't going into the booster.
     
  8. DesmoEd

    DesmoEd Veteran Member

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    I had the same problem on another vehicle - DP Holley covers the manifold vacuum port on Edelbrock intakes. Its Edelbrock's way to get you to run one of their carbs - the Edelbrock carbs will clear the vacuum port.

    Solution was 1/2 in spacer, low profile manifold vacuum fitting , and a drop base a/c

    I would not T off the PCV for brakes as the PCV system operates on a constant vacuum loss.

    On my '73 Camaro I am running two seperate 3/8 vacuum ports - one from base of carb and one via a ported spacer - for both PCV and P/B. Intake manifold vacuum handles everything else.

    Good Luck, Ed
     
  9. Lrader99

    Lrader99 Veteran Member Lifetime Gold Member

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    i would definitely run 2 separate lines as the pcv lines often have a very minute amount of oil in them. you do not want to introduce this into the booster lines, the oil can corrode and collapse the lines and clog up the check valve
     
  10. Todd80Z28

    Todd80Z28 Moderator Staff Member Lifetime Gold Member

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    Even though the PCV line seems like it has full vacuum, it doesn't, due to the relatively large air flow through the line from the PCV valve to the manifold. As such, any vacuum signal you tap off the line, depending on where you tap it, will be weaker than actual manifold vac.

    If you "T" it right at the base of the carb, you might get a strong enough vac signal, but otherwise, probably not. In fact, a "Y" out of the carb base probably would work better than a T.
     

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