rkinney

^^^This is true.

rkinney

^^^Very true.

Cross

iTrader: (10)

Which might be why a few ppl feel they get more power... they are running slightly leaner. But were not talking very much here...

buffman

iTrader: (9)

yes as I mentioned its not much air, and the PCM should be able to compensate for it. But in my case mine didn't. Mine would always want to die and you could see the BLMS were off. I put the stock hose back on and removed the breather and never had a single issue.

Formula413

iTrader: (1)

Does everyone know about the breather mod where you replace the elbow in the passenger side valve cover with a purolator breather? Helps keep oil from getting sucked into the top of the throttle body through the vent hose.

Cross

iTrader: (10)

I did not know about it... But I did it on my own thinking I was sucking oil in to my IM through there after pulling the TB and seeing oil in the IM.

I just used one of those chrome universal PCV setups so it could still be hooked to vaccum on the TB incase in was important.

The Engineer

That is the "fresh-air inlet" for the PVC system. By design, filtered fresh-air is pulled through the throttle body an into the passenger's side valve cover, then pulled back-out of the crankcase by the PCV valve.

However, when crankcase pressures build-up and the PVC system vaccum can't keep-up, hot oil gases are pushed back through the fresh-air tube (reverse flow) and into the throttle body.

WD

caldercay

A "one-way" valve (aka, PCV valve of some sort) could solve that issue.

buffman

iTrader: (9)

But that's not how it's designed to work. As he described it's supposed to go two ways.

caldercay

The way I read it is, "by design, filtered fresh-air is pulled through the throttle
body and into the passenger's side valve cover, then pulled back-out of the
crankcase by the PCV valve."

Yes, I read the "however" part, but I *think* that is mentioned because it's
a side-effect, not how it's designed. It's a given, since there is no valve.

I mean, really, would a Chevy engineer design an engine component to not
work under a worse-case condition?

Formula413

iTrader: (1)

Correct. The breather in place of the elbow on the inlet hose helps keeps oil from getting through that hose and into the throttle body and intake, while not interfering with the normal function of the hose. Cheap easy mod to help keep oil where it belongs, in the crankcase. Part number is Purolator B23165, available at Advance Auto. Autozone has a similar part made by Deutsch.

http://www.partsamerica.com/productd...tNumber=B23165

SS RRR

iTrader: (2)

It's not a vacuum leak. I understand what you're saying, but a vacuum leak is a directional event whereas a breather is for neutral flow, hence the term breather.

Formula413

iTrader: (1)

Perhaps a better way to word it would be unmetered air. It is air entering the engine after the MAF sensor (as with a vacuum leak), hence the PCM does not account for it and this creates a lean condition. The O2 sensors will see this and the PCM will try to compensate, but it will essentially be running around in circles. However this would not be a problem on an engine operating in speed density mode, such as '93 LT1s or any car that has been tuned to speed density.

I use the term vacuum leak to describe any opening that lets unmetered air into the into the intake manifold, is that not correct?

rkinney

^^^I agree 100%. I have a 93 and it is not an issue. Mass air cars will see a change in fuel trims.

SS RRR

iTrader: (2)

I guess it depends on how you want to think about it. I reckon it can be considered a "leak" when outside air does make it into the intake by other means than the MAF. I guess it can be considered an inconsistent "leak."
I would prefer calling it an unmetered air leak rather than a vacuum leak.
Several years ago before we knew any better a friend of mine and I were running breathers when it was the "cool" thing to do and noticed no performance difference.

letsrun97z

iTrader: (7)

J/w whats the point of having LT's and keeping the A.I.R? im in cali and having Lt and no air is illigal

buffman

iTrader: (9)

the FSM describes and illustrates the two way function of that fresh air hose

Cross

iTrader: (10)

Hey I have that Holley TB I just ordered it lol.

Steve in Seattle

1) Don't ever run a breather AND a PVC... if the PVC valve sticks open you'll have a wassive vacume leak.

2) PVC serves a similar function as a breather without spewing oil-mist into your hood liner or on your engine.

If you have a LOT of blow-by (ie. rings gapped for N2O, boosted applications, excessive cylinder wear, low-tension rings, etc...) and the PVC just isn't cutting it anymore a breather can help you from blowing the dipstick out, but your best bet is a vacumn pump or a dry0sump oil system. Neither is cheap.

Breathers are just an easy/dirty fix to popping dip sticks or constantly-fouling PVC valves.

Steve in Seattle

So when are ya gonna reclaim some of that hp and get a vaccume pump? I assumed anyone willing to low-tension their ring package would jump at the hp gains

I'm seriously tossing around a few options, but a dry-sump oiling system is just too much cash.