Correct PCV set up?

[Dave_EH]

Hi,

I've been doing a little reading on PCV set ups, and to be honest such a simple thing is starting to confuse me. 

I'm running a KC rocker cover on a red six to allow clearance for roller rockers.  These rocker covers only have one hole at the rear for a PCV and one at the front for an oil fill cap.

I currently run a breathable filler cap, with the rear hole having a PCV valve and going into the manifold.

The rocker cover isn't baffled (which considering the cost of these covers is a bit rude). 

Should I be running an oil catch can?
Would I be better off using a walking stick set up?

This is the article I have read if someone has time to read it.  Its a bit of a hotch potch. http://holdenpaedia.oldholden.com/PCV

Cheers
Dave

[craiga]

Hi Dave,

I've been looking at this exact issue - every highly modded engine that I see uses multiple crankcase breather pipes instead of a PCV valve.

These breathers are as follows:

Two in rocker cover
One, sometimes two into sump
One, sometimes two into sideplates

These breathers are then routed to a 'catch can' which is vented to atmosphere.

For street use though a PCV valve should be effective enough. I use a catch can between the rocker cover mounted PCV and the centre manifold (triples) only to remove the pulsations created by engine air intake which caused the PCV to rattle at idle.

I hope someone else has advice in this area as it will make interesting reading.

Cheers,

Craig.

Cheers,

Craig.

[Ed]

Hello,

PCV is such a black science...

That Old holden article is good and informative.

The breather cap should be letting air IN to the motor as it is pushed out the PCV side of things.

Similarly, on the Holden V8 (EFI on) excess gasses are sent out the RHS rocker cover, meanwhile air is sucked in from the LHS. 

The excess gas can either be recyled thru the intake manifold, or vented via a catch can to atmosphere.

Using a catch can traps the heavy oil in the excess gas so it doesnt go out into atmosphere or back into the motor.

At the moment I am running no PCV valve so there is always vacuum thru the motor and recyling the excess thru the intake.   I should be running a PCV valve otherwise the motor will get excess carbon.

You can run no PCV valve and straight to catch can which is vented to atmoshpere and block up the vacuum port on the intake, and still use breather oil cap.

in the case of the 308, I am considering running both out and in hoses both to a vented catch can, where it can exhale into the can and inhale from the same can... Build up of pressure should be avoided as the can will be vented (via breather) to atmosphere.

that's my understanding anyway...

I found out by accidentally joining the exhale side to the inhale side on a motor with bad rings... the result was oil blowing out the dipstick tube.

hope this is of some help.

Cheers

Ed

[NO NAME]

While on the topic,
 i am using a catch can, it has one inlet and one outlet to a breather filter, i could have ordered my rocker cover (fabricated aliminium sheetmetal) with two breather pipe holes but only ended up getting one, i didnt realise they put baffles behind the holes.
 could i also run a hose to the fuel pump hole in the block and would it be much if any advantage and could i just run a t peice between the fuel pump hole hose and the rocker cover hose to the catch can inlet?
 would it have to be a screw in fitting at the fuel pump hole?

[Ed]

I reckon one breather hole should be enough.  You shouldnt be really getting that much pressure build up if your rings are in good order??

I always thought the return line to the fuel pump block offs were just drain lines to return oil back to the sump, rather than having to empty the can... I could be wrong though.

A non leak fitting which wont vibrate out is a must.

check out some cool catch cans here.

http://www.iprraceproducts.com


Cheers

Ed

[craiga]

This is typical of what i have seen in high performance red 6's.

Drag type engine.



Circuit Car



FWIK red motors, when used at high revs, generate significant crankcase pressures and this is relieved by venting to atmosphere using the controlled environment of a catch can.

Note: All credit for pictures to original owners (gmhtorana.com/australianmusclecarsales.com.au)

[Ed]

Why is it that most commercially available catch cans come with 3/8" NPT inlets when most PCV outlets are around 5/8"?

trying to get a can with 5/8" inlets.....