How much blow by???

[SethSwitch]

Hello,
I know all engines have some blow by but today I noticed that a decent amount of air is coming out of my crank case vent. I don't know how to give a good idea of how much air is venting into the intake, but I would assume that about a gallon is venting every 2 minuets at idle. Should this be a sign that piston rings are going out or is this typical for the 5.3?
Thanks,
Seth


2010 Tahoe LT : 3" lift, catch can, cold air intake, Magnaflow muffler, SLP resonator delete

 

[Buzzcut]

A gallon of what venting?

 

[undy]

The standard of measurement for air movement is CFM (cubic feet per minute).

How many miles on the engine? Is it tuned? How much oil are you getting in the catch can?

You shouldn't be getting much perceivable air flow. Are you sure you piped in your catch can correctly?

 

[Buzzcut]

Catch cans aren't really needed on a naturally aspirated engine.

 

[SethSwitch]

The standard of measurement for air movement is CFM (cubic feet per minute).

How many miles on the engine? Is it tuned? How much oil are you getting in the catch can?

You shouldn't be getting much perceivable air flow. Are you sure you piped in your catch can correctly?

I would assume .33 cubic feet per minute. I don't get any oil in the catch can but it is tuned with 95,000 miles. I am positive that it is connected correctly and Justin checked it when he tuned the vehicle. It hardly burns oil so I'm hoping that this is just how these 5.3s are but wanted to get some opinions.

Seth

 

[bottomline2000]

Catch cans aren't really needed on a naturally aspirated engine.

Why would you say that?

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[Buzzcut]

Why would you say that?

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If it was required the manufacturer would have it. Just google it and you can decide for yourself. I used to race my mustang and was N/A. I never bothered as the HP level I was at and lack of supercharger wouldn't force more blow-by that would make a catch can useful or needed. I have yet see a catch-can in a normally maintained engine have any amount other than a wetness in it. Significant blow-by indicated by "larger" quantities of oil meaning it is only a band-aid to a larger issue.

YMMV

 

[undy]

If you're getting that much blow-by I'd have a leak down test performed. If your tune is off and had some detonation you could have a busted ring land or burnt valve. The stock hypereutectic pistons are very brittle and WILL NOT tolerate detonation.

The statement that NA engines don't need catch cans is totally absurd. LS engines are notorious for ingesting oil into their intake tract stock and especially when modded. The catch can minimizes combustion chamber deposits and carbon buildup on exhaust valves. I'm running one on my Z06's highly modded N/A LS7.

 

[bottomline2000]

If it was required the manufacturer would have it. Just google it and you can decide for yourself. I used to race my mustang and was N/A. I never bothered as the HP level I was at and lack of supercharger wouldn't force more blow-by that would make a catch can useful or needed. I have yet see a catch-can in a normally maintained engine have any amount other than a wetness in it. Significant blow-by indicated by "larger" quantities of oil meaning it is only a band-aid to a larger issue.

YMMV

Well I can tell you from personal experience the ls based motors need a catch can. If you ever pull the intake off one of these trucks you will see its full of oil. A lot of us are running catch cans n/a and routinely pull 50-100 cc of oil out of our catch cans between oil changes.

Our pvc systems have a design problem and I'm sure GM is aware of it but since you can get 100k out of the stock design before cats start to fail and buildup becomes a problem they simply didn't bother. Look at the "get a catch can before any mods" thread. That's all the proof u should need.

EDIT..didn't see the post from Undy until after my response..pretty much sums it up..

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[Buzzcut]

If you're getting that much blow-by I'd have a leak down test performed. If your tune is off and had some detonation you could have a busted ring land or burnt valve. The stock hypereutectic pistons are very brittle and WILL NOT tolerate detonation.

The statement that NA engines don't need catch cans is totally absurd. LS engines are notorious for ingesting oil into their intake tract stock and especially when modded. The catch can minimizes combustion chamber deposits and carbon buildup on exhaust valves. I'm running one on my Z06's highly modded N/A LS7.

If you aren't supercharged it is nothing but eye candy. But that's my opinion. You won't convince me otherwise. Been playing the hot rod game for over 30+ years and never bought the trendy catch can game over the last 10+ years. Since you called it absurd thought what data do you have the proves your point? My 170K 03 Tahoe used no oil between changes. I was my wifes DD. It would tow or haul and knock out 19-20 hwy. Changed the plugs at 100K clean as a whistle.

As I stated YMMV. What you use is great for you but I stated my opinion. You may not agree but that's life.