Valve cover breather
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Junior Member
Joined: Mar 2015
Posts: 12
Likes: 0
From: PA
Car: 1988 Camaro IROC-Z
Engine: 5.0
Valve cover breather
On the passenger side do i need to run a hose from the valve cover breather to the throttle body? or can i just install a breather without a hose and cap off the port on the throttle body? any negative affects of doing this?
Supreme Member

Joined: Jul 1999
Posts: 1,556
Likes: 28
From: Adrian, Mi, USA
Car: 1988 Pontiac Firebird Formula
Engine: 5.7 TPI
Transmission: 700R4
Re: Valve cover breather
If your breather has a filter in it, shouldn't be a problem. Just don't want to be sucking dirty air into the engine there.
Joined: Jan 2009
Posts: 887
Likes: 17
From: Golden, CO
Car: 87 IROC
Engine: L31 350
Transmission: T56
Axle/Gears: 4.10 D44
Re: Valve cover breather
@rmertus - If you have a MAF TPI system, what you are proposing is a "vacuum leak". You will be letting unmetered air (not measured by the MAF) into the crankcase, through the PCV and into the intake manifold.
If you are running a carb, TB or SD TPI, you are probably OK.
If you are running a carb, TB or SD TPI, you are probably OK.
Re: Valve cover breather
the factory setup has a larger diameter hose that runs from the throttle body to the right valve cover. that means it's air that's accounted for by the MAF. Air coming in from a breather cap is not. Sort of a PITA, but it does matter at idle.
Re: Valve cover breather
re-reading my post, I should have made it clear that the "breather air" or PCV inlet comes from the throttle body, but from in front of the throttle plates. it's not a vacuum leak. It's the larger 1/2" hose nipple on the right side, angles down slightly. It's the only hose nipple that big I've ever seen on a GM carb or throttle body.
It appears that the air foil that's mounted on my throttle body restricts the flow volume through it, I need to look at that before buttoning up this basket case TPI I"m building here.
It appears that the air foil that's mounted on my throttle body restricts the flow volume through it, I need to look at that before buttoning up this basket case TPI I"m building here.
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