Oil out of the Vent Tube

[jtybt]

Re: Oil out of the Vent Tube

http://wiki.gmnext.com/wiki/index.php/1963,_The_PCV_Valve,_a_"Green"_Breakthrough





A more common cause of blow-by is worn valve guides.

Fact of the matter is boats motors aren't going to be putting that many hours to cause ring and cylinder wear that would lead to blow-by ...UNLESS the engine wasn't properly broken-in and the cylinder walls were glazed and the rings never seated.

Moly filled rings seat faster and require a different hone/grit.

 

[JustJason]

Re: Oil out of the Vent Tube

If he does have a PCV valve on the engine someone would have added it, as it would not have come stock. All that's on the 3.0ls is a brillo pad in the fill cap or a plastic elbow vented to the flame arrestor.

My old 1975 888 has a PCV valve --- just wondering why some boat engines do not have one --- I can not think of a reason not to have one

Because the plastic elbow was replaced by a PCV valve at one point along its life by a previous owner. The elbow is fine.

The reason for a PCV is to help keep contaminents out of the oil, it has nothing to do with emmisions.

Thats actually not true at all. All a PCV valve does is this.... When you heat oil, any kind of oil, it fumes. Those fumes are noxious, polluting, and they don't smell all that pretty. When the engine is running crankcase pressure opens the valve and vents the fumes into the engine to be burnt along with the rest of the gasses. When the engine is off there is no crankcase pressure and the valve closes, and traps the fumes and the odor inside of the engine. That's all it does. It is in fact for emission control, and because marine engines are not subject to the same laws that govern automobiles they are not required by law to add them. (Yet)

They have been on engines since the 50's for sure and probably longer than that.

That is not true either. PCV valves are mandated by the EPA. And since the EPA wasn't formed until 1970.... well you get the picture. Heck GM didn't even invent the PCV valve itself untill almost 1960. So Marty McFly... who got in their delorean and started installing PCV valves on engines 10+ years before they were even invented... let alone mandated??

IMHO -- boats should have their fuel vapors run to a carbon canister --- one way check valves --- sealed gas tanks etc.,

You obviously do not understand the boat building process. Besides... you think boats are expensive now??

To the original poster....

There is a slight bit of oil coming out of the vent tube that comes out of the top of the valve cover and hooks to the side of the carb

Define "slight bit" better... Are we talking you stuck your finger in the hose and it came out oily and black. Is the hose dripping oil on the manifold? Is it spraying oil everywhere???

 

[cr2k]

Re: Oil out of the Vent Tube

Wow is sure took a lot of posts to answer a simple question.

As stated one source of blow by is bad rings where the combustion gas (and energy) will slip past the worn piston rings in to the crank case increasing pressure inside the engine. Normally operating engine produces less blow by then the simple breather tube to the spark arrester can handle so you don't notice anything.

Probably what you have. Answer is: If it's still running good and you can afford to keep oil in it AND it doesn't leave an oil slick where you go. "Drive it 'till it pukes." Maybe a winter project to swap out a short block and have your heads done or just go long block.

Another is possible is worn valve guides. If it backfires when you pull the throttle off is a possible sign of this.

There are some additives out there that claim to help the problem, but generally they don't do enough to really help.

 

[bruceb58]

Re: Oil out of the Vent Tube

Everything you wanted to know about PCV valves but were afraid to ask.

http://en.wikipedia.org/wiki/Pcv_valve

 

[cr2k]

Re: Oil out of the Vent Tube

Another thing we missed....Sludge clogged oil return passages in the heads.

 

[Blujay96]

Re: Oil out of the Vent Tube

Thank you all for the information. Very helpfull. I will check the comprestion. There is no pcv just the elbow as listed above. I think I will make it a winter project.

 

[Apollo75]

Re: Oil out of the Vent Tube

The article is correct --- Thanks for posting the link.

PCV valve works as long as engine vacuum can overcome the PCV spring pressure. The breather tube going to the spark arrester from the rocker / valve cover does the same thing with higher rpm where a low pressure area is created and pulls the vapors out of the rocker / valve cover.

The OP has some blow-by --- he has a little oil by the breather tube --- I still cannot tell him to rebuild his engine on such little information.


OFM

 

[Blujay96]

Re: Oil out of the Vent Tube

There was about a teaspoon of oil sitting by the valve cover. You could see that it had splashed from the tube and there was a slight bit in the tube. It was not black, but looked very clean just as the oil does on the dipstick. I check the oil everytime I go out and have not noticed the level go down.

 

[Apollo75]

Re: Oil out of the Vent Tube

Good --- If your not fouling plugs every half hour and the blow-by is not excessive --- Go Fishing


OFM

 

[Blujay96]

Re: Oil out of the Vent Tube

I like the sound of that.

 

[howlnmad]

Re: Oil out of the Vent Tube

The article is correct --- Thanks for posting the link.


The OP has some blow-by --- he has a little oil by the breather tube --- I still cannot tell him to rebuild his engine on such little information.


OFM

That's easy. Time to pull the motor, send it out and have it bored .030 over and honed, buy new pistons and rings and have the head redone (honed valve guides, new valves and seals). See, it was just that easy. Just kidding. If it's not a floating haz-mat issue and you can afford to keep oil in it... run it