uberstang1

So I've been pondering the thoughts of deleting my PCV valve, and just running breathers on both valve covers, whats everyones expereince on this? The oil seperator just didn't cut it and when I pulled my stock motor it appears a good amount of oil would still make it past it and I just don't want to run into that with the new setup. PS: Emmissions testing is not a concern.

oxfordgt

You won't like the smell of just breathers in the covers.

Run a line from both covers into the fender and use a catch can and filter there. It will keep down the smell and keep engine bay clean.

cliffyk

It all depends on vehicle use, in broad strokes:

• On a mostly short trip, around town, short commute (<15 miles each way) DD, absolutely not;
  
• On a longer commute (>20 miles each way) DD, I wouldn't but that's just me;
  
• On a weekend racer/cruiser, low weekly mileage, (but keep the oil clean)--go for it;

uberstang1

I must say my knowledge on the emission equipment is lacking, Cliff why do you say not to do it, what exactly does the PCV function as, I imagine it releases crank case pressure and gasses but from a mechanical standpoint what kind of negative effects would be had of just venting it to atmosphere compared to recirculating it back into the intake.

oxfordgt

The PCV creates vacuum in the crankcase which evacuates gasses out and helps to seal the rings.

What I'm sure he is referring to by what he said is condensation in the crankcase. If you drive short distances and not allow the engine to get to operating temp condensation can not get out and will cause sludge. This is true but it is also true with a factory PCV working. The key is to get the engine to temp. I drove my car every day to work(10-15 min drive) and never once had a problem with condensation or sludge. The engine always warmed up plenty to evac it thru the breathers. Now this is only because the car is EFI. All cars have a cold drive off map in the computer which makes the car run richer and warm up faster. If you had a carb engine with no electronic choke (race car) then no I would not suggest just running breathers because you will get sludge.

cliffyk

The PCV system forcibly withdraws and disposes of (by re-burning) gaseous combustion by-products, including acidic, alkaline, and water vapours, which would otherwise only be ejected by the pressure of the piston ring blow-by, and whatever was ejected when the piston's motion created pressure in the crankcase.

However the more cylinders you have the more the up and down motion of the pistons cancel out any net crankcase pressurization caused solely by the engine's mechanical activity within the crankcase.

This, as oxfordGT says, makes it more critical on an engine that is never run long enough to boil off these nasties--what they then do is condense in the crankcase, and cam/valve covers, each according to its own saturation limit (I.e. "dew point"). If the oil never gets hot enough to boil them off they stay there and form sludge.

However an active PCV system sucks these gasses out using manifold vacuum (this typically happens when the engine is idling or running under moderate and constant load), drawing in clean air at the same time--it works best in combination with proper engine operation; but it's better than just breathers even if the engine is never run hot enough to boil off the crap.

In the old days all engines had were valve cover breathers and big V8s run exclusively around town to do errands would sludge up in 20-30k miles...

ZeroTX

In other words, to remove the PCV system would be just plain retarded and would gain you zero hp... why do that?

oxfordgt

It's not retarded. You remove it on boosted engines to keep oil out of the intake. It cuts down on detonation and stops dead air (crankcase gasses) from entering the cylinder allowing more a/f mixture to enter and make more power. You will never see a PCV system on a race car they will either have a vacuum pump or evac system. I had an evac system on my race car to seal the low tension rings.

disposablehero27

At what leve of F/I would you consider using these? 10/12psi? I'm aware psi is a level of restriction, but we all know thats a close to basic setup. I was thinking f series procharger, turbo'd with 30psi etc. Higher levels.... should I be running these with a P/D1sc at lower levels?

oxfordgt

When I built my buddys 01 it had a D1 on 10lbs and made 535rwhp. We kept the PCV system but modified it with an oil separator and used a PCV valve from an SVO turbo car to keep from boosting the crank case. Worked well as long as he watched the fluid level in the separator.

Keep your PCV and check your intake after a few hundred miles. If there is oil in it and you have done your best to modify the system then delete it. But if there is no oil leave it.