engine breather

[DUBLE PUMPER]

Ive just put a new chevy zz4 385 bhp engine in my sport
ive vented the rocker boxes through a catch tank to atmosphere .no valves.
Ive just done about 150 miles at a track day and ive got about 1 1/2 pints of oil in the tank. the engine is running great.
anyone got any ideas ????

[barroom_spert]

Have your rocker covers got a baffler inside wher your pipes vent to the catch tanc?

Culd also have some blow by before the rings bed in full. What milage have you don?

[tuxman]

are you running a accusump ,this when operated can cause overfil which can lead to some venting out of the breathers . simon

[US-GTR]

Are you venting one or both rocker covers?

A stroked engine should have at minimum 2, some of the ones I have built I drilled and tapped the fuel pump block off plate. I then ran a hose from there to a catch can.

"Strokers" require more "breathing" than most engines due to the displacement under the piston.

[DUBLE PUMPER]

Ime not running an accusump but have got a u weld it baffled sump modification .
The engines only done the 150 miles so it is possible that there is some cc compression till the rings bed in.
There is one 1/2" rubber breather pipe stuffed in to the grometted opening on each of the rocker covers these are teed together and into the catch tank.
Ille check the insertion length of each and try adjusting it.
Thanks for your comments

[menostig]

I've got the same rubber hosiery on my ZZ4 engine. They go unfiltered from the rocker covers into a T and up into the air filter. This I suppose rebreaths it ?

It works ok but the underside of the K&N air filter housing is always filmed in oily crap.

Is this the right way ?

cheers
Rog

[steve_D]

I've just fitted a PSV valve to mine in the hope that my oil leaks are CC pressure related. Not had a run since so no answers yet.

Steve

[US-GTR]

DUBLE PUMPER said:

There is one 1/2" rubber breather pipe stuffed in to the grometted opening on each of the rocker covers these are teed together and into the catch tank.

Are both of the hoses (from each side) the same size as the one they "T" to? Each hose should have its own run to the can. Or, the hose they connect to must be able to carry the volume of air that BOTH of the primary hoses have.

Mr. Gasket has a crankcase breather that separates the oil from the air without restriction. Maybe a UK supplier has something like that (Demon Tweeks??).

Adding the PCV valve is a good idea depending on the volume of air that needs to be evacuated. Standard 350's can use one OK, but higher displacement engins move to much (under piston) air for a PCV to be effective. Having a "swirl pot" between your crankcase and your breather is about the best solution without getting a dedicated crankcase evacuation system.

[steve_D]

US-GTR said:

.....Adding the PCV valve is a good idea depending on the volume of air that needs to be evacuated. Standard 350's can use one OK, but higher displacement engins move to much (under piston) air for a PCV to be effective. Having a "swirl pot" between your crankcase and your breather is about the best solution without getting a dedicated crankcase evacuation system.

Do you think that the PSV will not be able to deal with my 407? I had the standard factory system with a pipe from each cover into the catch tank and 2 pipes from there out to atmosphere. I have now closed one of the exit pipes and connected the other through the PCV into the carb base. From what you were saying I may have made things worse.

Steve

[mclark]

Interested to see how this thread goes, as my engine builder actually recommends not running a breather box (as per factory) and to just use the two PCV vents.

Don't you have to fit a breather box if you have an Accusump fitted?

Michael

[pb3]

The breather should be collecting condensed water/oil vapour, nothing else, like catching oil that is being pushed out. In any case the Accusump should not affect this situation, after all it is only an alternative oil pump of sorts. Without baffles on the top two rocker cover takeoffs I could well imagine oil getting to the catch tank which is bad. I started a thread on this subject a while back “CRANKCASE BREATHER(S)” and I added a third breather take off from the fuel pump takeoff plate. I had two extra ports welded onto the catch tank, one for the new pipe to the new takeoff plate and one for an extra vent to atmosphere. So far so good and no oil leaks or oil in the catch tank, other than the slimy water as expected. As stated it is important not to restrict flow, that is why I added two extra ports, I was going to do a T but then thought that would just negate the extra takeoff!

[DUBLE PUMPER]

Ive 2 X 1/2 " pipes teed into a further 1/2 ' pipe into the tank.
the tank is vented with another 1/2" pipe. This is known as a1/2" job !!!

On my old engine i used to run the pipes into the cab side of the filter but was told catagorically not to do this by Real Steel and to take out the pcv s so i did and it was ok.

Think ile try getting some ally rocker covers that are taller than the tin ones and fit some baffles under the breather holes
Thanks for the info DP

[barroom_spert]

You shuld really run two large pipes to the catch tank and two 1/2 inch running into one 1/2 inch into the tank sounds too small.

As I said in the first post the baffles are absolutely vital.

I'm still worried about the quantity of oil you caught though. Lets here the outcome when you have the baffled rocker covers.

[steve_D]

DUBLE PUMPER said:

Ive 2 X 1/2 " pipes teed into a further 1/2 ' pipe into the tank. the tank is vented with another 1/2" pipe. This is known as a1/2" job !!! On my old engine i used to run the pipes into the cab side of the filter but was told catagorically not to do this by Real Steel and to take out the pcv s so i did and it was ok. Think ile try getting some ally rocker covers that are taller than the tin ones and fit some baffles under the breather holes Thanks for the info DP

You can buy grommets, that fit in the cover, that have a baffle moulded into them.

Steve

[menostig]

Double Pumper said: On my old engine i used to run the pipes into the carb side of the filter but was told catagorically not to do this by Real Steel and to take out the pcv s so i did and it was ok.


Well this is the setup on my ZZ4 so I rang Real Steel and they said it was just a matter of preference and wouldn't advise one method over the other. So am sticking with what has worked fine.

[US-GTR]

[quote]Do you think that the PSV will not be able to deal with my 407? I had the standard factory system with a pipe from each cover into the catch tank and 2 pipes from there out to atmosphere. I have now closed one of the exit pipes and connected the other through the PCV into the carb base. From what you were saying I may have made things worse.

Steve[/quote]

The set-up that I was reffering to is just a "vent to the atmosphere" type of system. What you have done is placed the crankcase into a negative pressure environment (read vacuum). Which is perfectly fine as long as your engine is not new and/or has lots of blow-by. However in DUBLE PUMPER’s case, he has too much air flowing from his crankcase (or so it sounds), either from a fresh motor or physical damage. Eventually changing to a system such as yours would be beneficial, unless you have a dry-sump oil system.