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Old 05-04-2004, 01:37 PM
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Where to drill the manifold

I have to drill the manifold to put a vacuum for my brake servo - the issue is where do I drill it - in a runner or directly under the carb ?

My thought is to put it under the carb as this will have more consistent and more vacuum than in one runner alone.

Opinions greatly appreciated.

Mark

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Old 05-04-2004, 02:18 PM
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If the tap was for a net inflow of gas like a PCV, it should go in the plenum under the carb to distribute the gas evenly. For an application like brake booster or vacuum advance that doesn't transfer any gas, any convenient tap in the manifold is fine. The vacuum signal will be just fine.
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Old 05-04-2004, 10:23 PM
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I have mine drilled on the back just under the carb. I dont really know why but thats how it was when I bought the car
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Old 05-05-2004, 08:18 AM
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I don't think I'd drill the manifold! I'd try to fine a spacer under the carb with a vac connection already there. OR drill & tap the spacer. Drilling & tapping a manifold, in place is a pain to do and get it right (straight). That plus you have to fight the metal shaving in the engine too. Seems to me dealing with a space would be LOTS easier. My $0.02, Good Luck! ...Mark
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Old 05-05-2004, 08:36 AM
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Thanks - if I had room I would, but it's a cobra and I've only got 3/16 clearance already !!

Some people (not on this forum) are telling me that T'ing into the brake servo line is OK and I don't have to drill and tap the manifold - won't this reduce the vacuum available to suck in the PCV gases
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Old 05-05-2004, 08:49 AM
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I'll give you my opinion on it...I don't know what type of power you have but let's say it is origional FORD with a not very common (scarce) intake. I would do anything to keep from modifying that intake. I would tee the booster signal into the PCV vacuum inlet and see if that will be acceptable. It should not interfere with the PCV system and should provide enough of a vacuum signal to operate the booster.

If you are worried about engine vapors being drawn into the booster line, in-line vapor traps are available. You might want to verify vacuum signal (and correct booster operation) after the installation with a gauge and monitor the PCV system for awhile (blow back on the inlets) to make sure it is fully operable.

The only time you will be deterring the PCV signal is on brake application.
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