pcv or evac:which is better for drawing vaccum?

Old 01-23-2008, 08:12 AM
  #1  
russ67chevelle
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Default pcv or evac:which is better for drawing vaccum?

pcv from valve cover to intake or evac from collector to valve cover....what are the diffrences on a bbc with a single plane,dominator set up with a plate.my exhaust is free flowing(no chambered mufflers).



goal: to make cheap mans vacuum pump.....ideas???comments???thx in advance!
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Old 01-23-2008, 08:47 AM
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v8Fiero
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at WOT I would think header collector to valve cover would give more vacume. pretty much the same as how a carb works with Bernollis principle.

edit, at idle a pcv probably draws more vacume.
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Old 01-23-2008, 06:32 PM
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GLADIATORINC
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Has anybody tried electric vacuum pumps? There's a guy on RJ selling them for $160. Unless I come across a deal at a swap meet for a mech. pump I will be running the valve cover to collector. I have a motor plate that might make mounting the mech pump a challenge.
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Old 01-23-2008, 09:25 PM
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cepx111
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Moroso makes a evac kit for about $40 Its the valve cover to collector type, works great at WOT which is when you need it most.
><Cp
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Old 01-24-2008, 01:07 AM
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edvancedengines
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Use both at the same time.

By theory when one is open the other will be closed.

PCV is open only at times of high vacuum. Pcv is closed during full throttle. Crank evac system is mostly closed at high vacuum and is open when at low vacuum.

Ed
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Old 01-24-2008, 01:40 PM
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caprice327
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This is the exaust setup I have:

Long tube headers > 3"-2.5" reducer > 2.5" H pipe > 2.5" delta 40's with 3" pipes going all the way back.

Now lets say I properly installed the collector evac kit and ran both of them to one valve cover and the other valve cover would have a hose running directly to intake vac. Does that seem ok?

Should I add a pcv valve, seporator, one way check valve?

http://www.racingjunk.com/gallery/profile/255255
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Old 01-24-2008, 08:31 PM
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olds48
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Originally Posted by edvancedengines
Use both at the same time.

By theory when one is open the other will be closed.

PCV is open only at times of high vacuum. Pcv is closed during full throttle. Crank evac system is mostly closed at high vacuum and is open when at low vacuum.

Ed
How would you go about plumbing in a setup like that.To pull off one v/c with a pcv,doesn't the other have to have a breather so that it draws thru the engine?Looks like you would need 4 breather holes that way.Not trying to dispite you,just honestly curious.
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Old 01-24-2008, 10:18 PM
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cepx111
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The only thing I dont like about a pcv system is the oil vapors that are pulled into the intake plenum and intake ports valves etc, which leave nasty flow inhibiting deposits. Rather crap that junk out my exhaust and say adious.......
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Old 01-25-2008, 07:35 AM
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russ67chevelle
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i kinda agree with suckin into the intake tract oily fumes is kinda icky-is it a concern? if not,where to plumb into on my dart tall deck intake?by the way ive also got a nitrous plate kit on...what is opinions of electric vacuum pumps?if i just run evac to header is it ok to just use one valve cover lined down to one collector(cause i have air to fuel ratio sensor welded in one collector already)
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Old 01-25-2008, 07:29 PM
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caprice327
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:idea: So when is someone going to step up to the plate and get a patent on a AFFORDABLE electric or belt drive evac pump for the high performance street guys and become a multi millionaire?

I would do it but I dont have the funds to get it started
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