F'in PCV System

**Sweet Chops** · 11-25-2007, 07:08 AM

I noticed when i put my Car away for the winter that there was some oil in the top left corner of the throtle body. It is coming from the breather hose on the passenger side valve cover that plugs into the throtle body. I have a AMW catchcan, but I have the PCV tube that comes from the back of the engine pluged into it before the PCV valve. I was wondering if I tap a second in and out in the catch can for the valve cover breather tube it will help my problem, or will it give me problems because there are diffrent pressures in both PCV tubes. Need some options.

Car- 99Z M6 50,000 miles
Mods- K&N FLPK, GMMG Exhaust

Thanks
Ryan

**Sunset T/A** · 11-25-2007, 02:16 PM

Your PCV line from the right side should be hooked up to the TOP fitting on the catch can.

**Sweet Chops** · 11-26-2007, 07:00 AM

The catch can isn't the problem, it is the breather tube that comes from the pasenger side valve cover and plugs into the throtle body. It is sucking oil from the valve cover and I noticed the oil in the throtle body.

Ryan

**Sunset T/A** · 11-26-2007, 01:31 PM

Sounds like the catch can is not doing it's job. Yes, oil will come through that tube, but the can must catch it, until it gets full.

**Sweet Chops** · 11-27-2007, 06:58 AM

OK OK OK, now I get it air flows from the throtle body to the breather. Not the other way around. So if my catch can is hooked up backwards or it is full I will get oil in the valve cover breather hose.

Thank you sunsetta

Ryan

**ggino85** · 11-27-2007, 02:47 PM

where is a good write up on how to install a catch can. i looked in installuniversity but that one wasnt for a catch can it was something else with the pcv valve. thanks in advance

**Olde Skoole** · 11-27-2007, 04:22 PM

positive crankcase pressure is proportional to engine RPM, this pressure must be effectively vented to atmosphere, funny things begin to happen when crankcase pressure becomes excessive: the dip-stick may pop out among other things, it's been known to blow seals as well.
positive crankcase ventilation was needed to equalize this internal engine pressure while still keeping the pug-nosed enviromentalists at the EPA happy.
So the automotive industry discovered that by using the inherent engine vacuum that is inversely proportional to engine load the oil vapors could be recycled thru the intake tract, as a added benefit the oil vapors provided a little top-cylinder lubrication for good measure.
So we have learned that crankcase pressure increases with RPM and engine vacuum decreases with increased engine load....in case you fell asleep during the movie, there's something wrong with this picture and i will explain it to ya.
Positive Crankcase Ventilation can be highly effective at cruising speed when engine vacuum is high, however when you mash the go-pedal engine vacuum drops to zero, and crankcase pressure increases because the PCV system is out to lunch until your right foot lifts.
Early 3rd Gen LS1 valve covers are shorter than later models and require the baffle to be removed along with some die-grinder action to make room for increased valve lift via high-ratio rockers or high-lift bumpsticks.
Well now, we just fixed one problem and created another, the baffle was put there to keep oil from entering the PCV system, neccessity is the mother of invention so on the 8th day God created the Catch-Can.
It is suppose to "catch" the oil that gets sucked up by the PCV thereby allowing only oil vapors to reach the intake tract....
HP engines require a breather on each side so you wanna have a 3-way with the left and right valve covers and piped in the intake manifold,
I'm wild n out.