Valve Cover Vents and PVC

I am experiencing strange idle and looking to reduce possible problems.
LS6 with mid to large cam. I installed a LS2 throttle body on the FAST 92mm intake. I have a 2004 valley cover with the port that I connect my PVC value to then it connects to the FAST intake after the throttle body.

I have the stock valve covers which have an air vent on each. Should I plug the valve cover vents or leave open to the air. I would imagine that they should be closed and just allow the PVC vent the engine. Any opinions.

BTW, no air pump, emission stuff, no cats, no mufflers.

I am seeing high MAP readings at idle (50 to 75 KPa). I believe the pressure should be 30 to 50. I replace the MAP sensor and got same results.

A large cam will raise your idle kpa a fair bit. My 226/231 110 lsa cam idles around 63kpa.

BTW cam 248/254 110 high lift (1.7 ratio)

Side note: PCV valve - Positive Crankcase Ventilation (Vents Pressure)

PVC - PolyVinylChloride - Plastic pipe.

Quote:

---

Originally Posted by Stealth97

Side note: PCV valve - Positive Crankcase Ventilation (Vents Pressure)

PVC - PolyVinylChloride - Plastic pipe.

---

Its been a long day...

If the valve cover vents (you mean these tubes: see attached...?) are open then dirt will enter the crankcase...

Either somehow put a breather/filter on the vents... or connect up a flow-thru PCV system...

You can't just block the vents off...

The design of the PCV system is to allow fresh air to enter the crankcase, which moves/pushes blowby/condensation/vapour around so they can get pulled out into intake manifold... i.e. without air entering the crankcase, the crankcase will be under vacuum (negative pressure wrt baro) but there will be no flow... the crankcase won't be purged...

Usually the fresh air source is from the upstream side of the TB, and the drain is just downstream of the TB... across the TB is a pressure drop due to the butterfly (pressure is higher before the TB, and lower after the TB), so air flows from source to drain via PCV system plumbing... oh, and doing this means the MAF has counted this air.

using a breather/filter means the MAF has not counted that air... if you have no MAF it doesn't matter.

Quote:

---

Originally Posted by Rusty

Its been a long day...

---

Totally understood. Was just being a bit helpful =). I used to call it the PVC valve before I knew what it even did. Just knew my first car needed one the first day I got it (86 camaro).

When I was 15 (12 years ago), I thought Cadillac invented platinum substrate converters. I thought they were Cadillac Converters, not Catalytic Converters. Excuse me if auto mechanics don't pronunciate correctly, if at all. ;^) To be honest, I didn't know what a catalyst was until I learned how a converter works on vehicles.