Smokey 4.3L Engine via PCV valves

[CAPTahab7]

I have a 2003 Stingray with Merc 4.3 Carb 190A (Ser #M616646), I rebuilt the heads, replaced some valves after I blew a head gasket. I have it running now, but there is a good bit of smoke coming out the valve cover hoses that feed back into the intake. I thought it might 'burn through' as steam as I had water in oil, but have drained/replaced oil twice now. It definitey seems like smoke and I DONT see smoke coming out with the exhaust water. Engine seems to run fine, save for idle a bit rough (if I remove the smokey hoses from air intake it runs better). I have one piston right at the 100psi mark (a bit low and maybe blow-by from ring, so could be source of oil burn I suppose).

So my Questions:
Is a fair bit of smoke normal out the PCV hoses and NOT the exhaust at idle?
What would cause this (engine not have enough force to open back-flow flappers in exhaust at idle)?
Is there any down side to just blocking the PCV hoses wrt engine performance?

 

[Bondo]

Re: Smokey 4.3L Engine via PCV valves

So my Questions:
Is a fair bit of smoke normal out the PCV hoses and NOT the exhaust at idle?
What would cause this (engine not have enough force to open back-flow flappers in exhaust at idle)?
Is there any down side to just blocking the PCV hoses wrt engine performance?

Nope,... It ain't Normal...

It's probably from the scored cylinders mentioned in yer other threads...
You said they didn't look Bad, but obviously, they Are...

The downside of plugging those hoses is, the Pressure will be expelled wherever the motor can blow the weakest gaskets...

 

[paultjohnson]

Re: Smokey 4.3L Engine via PCV valves

What color smoke exactly ? Blue as in burning oil ? White, as in steam, or black, as in carbon-like over choke ?

As Bond-O said, if you plug the hoses, the pressure will find an escape route. However , you COULD just disconnect em from the intake and leave em lay there, and the pressure in the crankcase/valve cover will just vent to the atmosphere, Older engines used to just have a solid little tube comeing out of the valve cover with a chunk of foam on it. And/ or the oil fill cap on the valve cover was vented. You could then plug the intakes where the hose connects to the engine so you arent sucking air. However, thats not what you really want to do.... Band aid approach at best. Those PCV valve evacuate allot of the moisture/condensate oil laden fumes in your crankcase that will turn to SLUDGE if ya leave em in your engine...But it sounds like you have a bigger problem, unfortunately.

 

[Don S]

Re: Smokey 4.3L Engine via PCV valves

Do another compression test. Per this service bulletin http://www.boatfix.com/merc/Bullet/97/97_25.pdf
After the compression test, check the low cylinders per step 6 of the bulletin.

6. If some cylinders have low compression, use a pump type oil can to inject 3 squirts of oil into each combustion
chamber through the spark plug hole. Do second compression check on each cylinder.

If the compression comes up, the rings are not sealing for some reason. Scoring, wear, rust ...............

 

[CAPTahab7]

Re: Smokey 4.3L Engine via PCV valves

Thanks guys. I did another oil change (3rd one since blown gasket). Added some of that Rislone compression helper 'magic' to the oil. I then took the elbows leading off the cylinder covers and replaced with actual PVC valves. No smoke and its running well. I'm eager to try another compression test, but have not done so yet. Gosh, I might salvage some summer?!

 

[Evinrude Boater]

Re: Smokey 4.3L Engine via PCV valves

I then took the elbows leading off the cylinder covers and replaced with actual PVC valves.

Get ready to clean oil off the engine compartment when the dip stick pops out.

 

[CAPTahab7]

Re: Smokey 4.3L Engine via PCV valves

RAn engine for 30 min and so far so good. Evinrude Boater: Why do you think the dip stick will pop out? On a car engine the PVC valves don't create enough back pressure to cause that to happen. Also, shouldn't the smoke in the valve covers just go out the exhaust if no other place. Isn't that how motors worked BEFORE PVC valves were invented as an emission control mechanism?

 

[Gettinther]

Re: Smokey 4.3L Engine via PCV valves

RAn engine for 30 min and so far so good. Evinrude Boater: Why do you think the dip stick will pop out? On a car engine the PVC valves don't create enough back pressure to cause that to happen. Also, shouldn't the smoke in the valve covers just go out the exhaust if no other place. Isn't that how motors worked BEFORE PVC valves were invented as an emission control mechanism?

#1 On a car engine the PVC valves don't create enough back pressure to cause that to happen. Also, shouldn't the smoke in the valve covers just go out the exhaust if no other place. NO Thats because they are connected directly to manifold vac taking the crud into the engine and reburning it , also only one PCV valve per engine is necessaryin an automotive application. PCV valves do not belong in your boat If your PCV valves are not connected to a vac source then they are likely doing half the job they are supposed to by staying closed under no vac condition which will cause a crankcase pressure, which could cause the dipstick to pop and oil to spray all over , which could land on a hot engine and the next thing you have is a water front barbeque which you will become the hamburger.What I am telling you is that you have created a very dangerous situation for you and all of your passengers!!!!

I am not trying to be insulting and appoligize if I sound like it. I KNOW how these things work Please remove these PCV valves for your own safety

#2 Isn't that how motors worked BEFORE PVC valves were invented as an emission control mechanism? NO again they used to have a vent tube or similar device that directed the crud to the ground or road as it were but out of the engine never the less.

 

[CAPTahab7]

Re: Smokey 4.3L Engine via PCV valves

Thanks 'Getinthere' for the thoughts. I've been carefully watching how things go and can confirm that no ill side effects of having the PCV in place realized. I even 'manually' pluged the valve cover holes with thumbs to build a much higher pressure than the PCV valves would allow to test out your theory. There is simply just not enough force to push the dip stick/oil out. I understand your explanation and it makes sense logically, but it just doesn't bear up to reality. Appreciate the concern none-the-less.