pcv help !!
pcv help !! hey guys, this is my first post in the conversion section. i have a pretty simple question. ive been installing an LS3/2004r in a 72 camaro and have made really good progress in the last 6 months. cranked her for the first time on july 19th.its a gm crate LS3 that i did a cam swap(comp cams LSR 269-13/607-621/219-235 at .050 113} and a vic jr with fast ez-efi. anyway the LS# has 3 crankcase vents(one in each valve cover and one in the lifter valley). im trying to get ideas as to the best way tovent the crankcase. should i run all 3 vents? the fast throttle body has 2 ports in the back, so should i run 2 inline pcvs. is the vent in the lifter valley better than the ones in the valve covers? yall get the picture. thanks, david
TECH Apprentice
Joined: Feb 2011
Posts: 316
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From: Central Florida
The lifter valley has knock sensors - is there a crankcase vent there too?
You need an PCV source for low speed (idle) and high speed. The direction changes based on the RPMs. At idle the crankcase sucks and at high RPM the crankcase builds pressure. Most all factory PCV setups have one line before the throttle blades and one after.
You need an PCV source for low speed (idle) and high speed. The direction changes based on the RPMs. At idle the crankcase sucks and at high RPM the crankcase builds pressure. Most all factory PCV setups have one line before the throttle blades and one after.
The one in the valley is the one you want to hook to your vacuum source. It has baffles to try and cut down on the oil being sucked into the intake. GM went to the valley vent with the LS6 in an effort to cut down on the oil ingestion from the valve cover set up they used in the LS1's.
I hooked a PCV valve from the valley vent to the carb vac port. That gives the vac suction. You then need some type of vent to the atmosphere for outside air to get into the crankcase. The LS2 crate motor I have has a rubber plug in the vent hole on the back side of the driver side valve cover, and a 3/8 inch hardline coming off the passenger side valve cover. Instead of running that vent to the aircleaner (it needs to be filtered so dirty air doesn't get sucked into the motor) I just used a piece of 3/8 inch fuel line and a cheapo fuel filter on that.
Its is a very good idea to run a catch can between the valley vent and the carb vac. Oil in the intake effectively lowers the octane of your fuel and can lead to detonation.
Since the fast EFI doesn't run a MAF you don't need to worry about plumbing the crankcase vent to a metered air source. It is just like a carb in that sense.
I hooked a PCV valve from the valley vent to the carb vac port. That gives the vac suction. You then need some type of vent to the atmosphere for outside air to get into the crankcase. The LS2 crate motor I have has a rubber plug in the vent hole on the back side of the driver side valve cover, and a 3/8 inch hardline coming off the passenger side valve cover. Instead of running that vent to the aircleaner (it needs to be filtered so dirty air doesn't get sucked into the motor) I just used a piece of 3/8 inch fuel line and a cheapo fuel filter on that.
Its is a very good idea to run a catch can between the valley vent and the carb vac. Oil in the intake effectively lowers the octane of your fuel and can lead to detonation.
Since the fast EFI doesn't run a MAF you don't need to worry about plumbing the crankcase vent to a metered air source. It is just like a carb in that sense.
