PCV valve

Hi Josh. If you are referring to crankcase ventilation, Ferrari (as with many makes) normally refer to this as a "Blow-By System". The system for the 355 is illustrated in Table 18 in the work shop manual. Hope that this helps. Ron.

 

Josh,
How full are you running the oil tank, what is your checking procedure?
I know you've recently noticed increased oil consumption, so I would expect that you are doing it right. The crankcase valve(#42) commonly comes loose from the hoses, but then you'd notice oil on the side of the block.

 

The one way valve is easy enough to get to. You can remove it to check or replace.
Too bad I didn't have more time over the weekend, would have been worthwhile to bring my leakdown tester. Not to scare you, but sounds like typical bad cylinder liner symptoms- a leakdown would tell all.

 

The 355 does not have what you called a PCV (I take that to mean a valve in the crankcase breather system) - a breather system does not work with a valve - your second diagrm. There is, of course, a valve (non-return) in the lubrication system - your first diagram.

 

After the oil and vapors have separated in the oil reservoir (tank), the vapor is allowed to be sucked into the helmholtz resonators and down the intake velocity stacks with the air. If you get the oil tank too full, the liquid oil can be sucked directly into the helmholts resonators and you car will blow smoke until the oil lever returns to normal.

In this system there is no PCV valve and the crank case is never under pressure. This is one of the advantages of a dry sump system.

 

In a flat plane V8, when any one pair of pistons is decending, there is another pair of pistons acending. So, excepting for the minor volume change due to finite length conrods, the volume in the engine sump is quite constant. {This is NOT to say that there is not a lot of windage from cylinder to cylinder, there is. In addition there is a barage of oil being splayed from the journals and more from the piston squirters. This barage causes the windage to pummel all sides of the sump volume with a hot oily mixture.}

Then the 2 oil pumps in the dry sump pump more than just the volume of oil returning to the sump. They pump hard* enough so (that most of the time) they are picking up air and vapors** along with the oil. Given that the pumps pump more volume than the combination of return oil and pressure imbalances caused by the piston movements, most of the time the sump pressure is near zero.

So with an average pressure near zero, the seals don't have a hard problem when a puff of pressure comes by for a handful of milliseconds before returning to its long term average of zero.

Thje trick wth the dry sump system is that: if you pump enough oil+vapor volume, after deareation, you can just let all the vapors into the intake without no valving what-so-ever. The partial vacuum of the intake will pull the vapors off the sump. So you have essentially a closed loop system.

(*) Racing engines with dry sumps will pull a partial vacuum for higher power. I believe that the road engines are just trying for break even (i.e. zero) crankcase pressure.
(**) one of the prime resons that the sump has a deareator in it.

A PCV valve waits until that puff of pressure comes by, and then it releases this puff of pressure up into the intake system by a valve seat and a spring. Since the oil, air, and vapor have not been separated, the valve and seat opperate in a rather nasty environment, and is subject to dirty oil, blow by carbon, coking, and varnish. Thus, more oil gets into the intake with the PCV vavle architecture than with the dry sump architecture.

 

And thanks from me too for the explanation!