Catch Can disappointment pics inside

[iamdub]

Thinking about going old school with hoses vented underneath (Road Draft Tube).

Your PCM wouldn't like the huge vacuum leak it'd see!

 

[ivin74]

do they recommend mounting it that low ? most are above valve cover level

The reason I mounted it that low was to keep the oil from seeping up but its still seeping up, I don't believe it matters where the catch can is mounted as long as you don't restrict the flow of vacuum the engine needs.

 

[bottomline2000]

with that amount of residue wouldn't you see some in the hose from the catchcan? reason i asked is I run the same catch can and there isn't anything inside my hose. Its dry.. is your PCV valve working properly?

EDIT! OP, you have you catch can hooked up backwards...that's why you have oil in the intake..the purpose of the media is to capture the atomized oil and fuel in the air. Yours is capturing it right as it sucks the air back into the intake. you want the incoming air to be filtered so it drops to the bottom of the can and you pull the clean filtered air from the can.

 

[swathdiver]

Your PCM wouldn't like the huge vacuum leak it'd see!

What vacuum leak?

I've tried to remember how we modified the Buicks and I think we left the PCV valve in place which was in the bottom of the intake at the valley cover and its hose went into the vacuum block behind the throttle body on the upper intake manifold. On the passenger side valve cover, there was an internal breather with fibrous material in it and a hose that connected to the turbocharger's inlet bell housing. This breather was replaced by a K&N filter and the inlet on the bell housing capped off. My Oldsmobile diesel had the same setup on the same valve cover but the pipe went to the air cleaner and that was capped off too.

With that setup, our intakes were clean and pistons as spotless as the day they were put into the engine. I remember sometimes draining oil out of a customer's intercooler and how gross the compressor blades were on stock motors that hadn't been modified. We also capped off the lines and fittings that sent engine coolant into the throttle body.

Am I correct in saying that we do not have a traditional PCV valve on our Gen IV engines but rather tubing and restrictions built into the valve cover? If the intake and throttle body and air inlet tube after the mass airflow sensor are plugged, there should be no vacuum leak. But there would need to be at least a hose acting as a vent from each of the valve covers to allow the blow by gases to escape. Breathers could also be used as could a catch can with a breather.

I do not remember our engine bays being covered in oil or oil spray, could not have been as it would have shown up in the photos and we would not have done well in car shows. Don't think I would have tolerated the mess and cleanup back then. But we are not comparing apples to apples either. These LS engines may have more blow by.

 

[iamdub]

What vacuum leak?

I've tried to remember how we modified the Buicks and I think we left the PCV valve in place which was in the bottom of the intake at the valley cover and its hose went into the vacuum block behind the throttle body on the upper intake manifold. On the passenger side valve cover, there was an internal breather with fibrous material in it and a hose that connected to the turbocharger's inlet bell housing. This breather was replaced by a K&N filter and the inlet on the bell housing capped off. My Oldsmobile diesel had the same setup on the same valve cover but the pipe went to the air cleaner and that was capped off too.

With that setup, our intakes were clean and pistons as spotless as the day they were put into the engine. I remember sometimes draining oil out of a customer's intercooler and how gross the compressor blades were on stock motors that hadn't been modified. We also capped off the lines and fittings that sent engine coolant into the throttle body.

Am I correct in saying that we do not have a traditional PCV valve on our Gen IV engines but rather tubing and restrictions built into the valve cover? If the intake and throttle body and air inlet tube after the mass airflow sensor are plugged, there should be no vacuum leak. But there would need to be at least a hose acting as a vent from each of the valve covers to allow the blow by gases to escape. Breathers could also be used as could a catch can with a breather.

I do not remember our engine bays being covered in oil or oil spray, could not have been as it would have shown up in the photos and we would not have done well in car shows. Don't think I would have tolerated the mess and cleanup back then. But we are not comparing apples to apples either. These LS engines may have more blow by.

PCV setup on a boosted engine is far different than on a N/A, and the LS engine is set up much differently than the older engines.

Basically, the vapors move through the LS engine differently on one side of the engine versus the other. This is why you have the passenger side valve cover plumbed to the air intake tube (fresh air into the engine) and the driver's side plumbed to the intake manifold (PCV/oily air out of engine). This is why the catch can goes on the driver's side circuit. It works by one side being pressurized and one side under vacuum.

Chances are that if you capped off the PCV inlet on the intake manifold and routed the PCV outlet (from the valve cover) to a "road draft tube", the MAP sensor would ultimately detect the imbalance of the air going in versus air going out. Maybe a breather filter on the PCV outlet from the valve cover would present enough restriction to keep the pressures withing spec? But, you'd have to clean or replace an oily filter every few thousand miles. The engine needs the PCV system to not only let the crankcase breathe (don't wanna pressurize and blow out seals!) but to vent moisture and other gasses. The EPA doesn't want this venting to atmosphere, so it is routed back into the intake to be burned off. The problem is the LS engine produces a lot of oil mist as it is and it's exacerbated by the AFM functions.

So, you need the PCV system, you just need to scrub the air of the oily mist. If simply capping off ports and adding breathers were a solution, this would've been figured out and done many years ago (the LS is about 20 years old!) and catch can's wouldn't be such a "thing".

 

[ivin74]

PCV setup on a boosted engine is far different than on a N/A, and the LS engine is set up much differently than the older engines.

Basically, the vapors move through the LS engine differently on one side of the engine versus the other. This is why you have the passenger side valve cover plumbed to the air intake tube (fresh air into the engine) and the driver's side plumbed to the intake manifold (PCV/oily air out of engine). This is why the catch can goes on the driver's side circuit. It works by one side being pressurized and one side under vacuum.

Chances are that if you capped off the PCV inlet on the intake manifold and routed the PCV outlet (from the valve cover) to a "road draft tube", the MAP sensor would ultimately detect the imbalance of the air going in versus air going out. Maybe a breather filter on the PCV outlet from the valve cover would present enough restriction to keep the pressures withing spec? But, you'd have to clean or replace an oily filter every few thousand miles. The engine needs the PCV system to not only let the crankcase breathe (don't wanna pressurize and blow out seals!) but to vent moisture and other gasses. The EPA doesn't want this venting to atmosphere, so it is routed back into the intake to be burned off. The problem is the LS engine produces a lot of oil mist as it is and it's exacerbated by the AFM functions.

So, you need the PCV system, you just need to scrub the air of the oily mist. If simply capping off ports and adding breathers were a solution, this would've been figured out and done many years ago (the LS is about 20 years old!) and catch can's wouldn't be such a "thing".

X2

 

[swathdiver]

Chris, now that I've spent some time learning about the LSs system, the layout is not different than my old turbocharged cars. The difference now from then is that the actual pcv valve is no longer used, at least a replaceable part with a check ball.

Reading very old Corvette forum postings, those guys set their cars up like we used to. I reckon the use of catch cans comes from the younger generations being browbeaten over protecting the environment and companies under threat of persecution/prosecution should they advocate for defeating an emissions control device.

I have not done anything yet, still recovering from the y-pipe mess and still have to get that busted bolt out of the frame. But my thoughts are to go old school and see at some point.

Ohh Chris, Something you've mentioned twice and wanted but forgot to address. Unless I'm missing something, the crankcase is not metered by any electronics so open or closed (if isolated from the intake air) is not going to set off any codes.

 

[iamdub]

Chris, now that I've spent some time learning about the LSs system, the layout is not different than my old turbocharged cars. The difference now from then is that the actual pcv valve is no longer used, at least a replaceable part with a check ball.

Reading very old Corvette forum postings, those guys set their cars up like we used to. I reckon the use of catch cans comes from the younger generations being browbeaten over protecting the environment and companies under threat of persecution/prosecution should they advocate for defeating an emissions control device.

I have not done anything yet, still recovering from the y-pipe mess and still have to get that busted bolt out of the frame. But my thoughts are to go old school and see at some point.

Ohh Chris, Something you've mentioned twice and wanted but forgot to address. Unless I'm missing something, the crankcase is not metered by any electronics so open or closed (if isolated from the intake air) is not going to set off any codes.

I'm all for someone (you?) trying out a simple solution to completely seal the intake of all oily air, just so long as it lets the crankcase breathe sufficiently enough to not blow out seals, etc.

I apologize for any confusion, but I never meant to imply that the crankcase was metered by any electronics. At least not directly. The intake manifold is sucking on a tube that is directly connected to the crankcase volume through the valve cover/cylinder head/etc. The intake manifold has a MAP sensor that reads pressure and that PCV circuit between the valve cover and intake manifold plays a role in the amount of pressure the MAP sensor sees. If it's open, the MAP sensor sees a "leak" (loss of vacuum). If it's closed (plugged off), the MAP sensor sees a buildup of pressure from the crankcase fumes not going anywhere.

 

[bottomline2000]

Could be the location of the hoses. I believe the incoming air/oil mixture should be going into the tank and the filtered air should be exiting the can through baffle/filter media and out the top. JMO

Again..This is backwards..

Sent from my SAMSUNG-SM-T377A using Tapatalk

 

[swathdiver]

I apologize for any confusion, but I never meant to imply that the crankcase was metered by any electronics. At least not directly. ...If it's closed (plugged off), the MAP sensor sees a buildup of pressure from the crankcase fumes not going anywhere.

I don't think that's the case Chris. Both valve covers have hoses going to the intake and or throttle body. If one were to remove the hoses going to the intake and or throttle body and plug them off the MAP sensor has no connection now with the crankcase. In addition, new hoses fitted with breathers at one end and the other connecting to the valve covers could be used to vent the crankcase. Ideally these would be mounted upright and above the valve covers.