Oil blow by

[truckin 79]

My truck has some miles on it but runs fine except oil blow by. The crankcase filter in air cleaner gets fairly saturated. This is on the 79 350 and just wondering if there is a better system to use for oil blow by. I currently have EGR blocked off would this have any effect on blow by?
Thanks

[Corts60]

Engine is probably just tired bud. Anything besides a rebuild will just be a bandaid.

[Dead Parrot]

OEM system works pretty good. As mentioned, if the motor is worn, blow by can over power the PCV valve and also flow back though the filter. Don't think the EGR has anything to do with crankcase ventilation.

Make sure the PCV valve and hose is good and the port in the carb is clear. The carb passages can get clogged.

An oil soaked PCV filter won't hurt anything as long as it is otherwise fairly clean.

Make sure the valve cover the air filter is connected to still has the internal oil splash setup. Aftermarket covers often omit the oil splash piece.

If the motor is otherwise running fine, don't worry too much about it. An extra quart of oil every so often is generally a lot cheaper then a new motor or a rebuild.

[LT7A]

Seems like a good place to ask: is anybody using a catch can setup?

[truckin 79]

I think I will have to just invest in crankcase filters which most of the parts stores here do not keep in stock. So do most people get oil inside of air cleaner as well as some oil on the side of the air filter? How does a catch can work, I have heard people use these in higher HP set ups.

[LT7A]

The good catch cans provide a baffled container in the line from the PCV valve to their cleaner where the air is changing direction enough times for the oil to drop out of suspension and accumulate in the can and let the air continue on relatively oil-free into the air cleaner.

[Axle]

Does the '79 have a cat converter? If thats starting to plug up it'll blow oil out the breather, and it will do it for a long time before the cat becomes plugged enough to cause driveability issues. Had it happen with my '83, thought the same; motor getting really tired and blowing oil. Nope, months later its starting to get a bit lethargic and I can hear it in the exhaust. Plugged cat. Back to normal bit of oil blowback after that.

[truckin 79]

Hmm interesting I know these trucks had less then impressive HP but I have always felt something is holding it back. The truck passes emissions just fine but really low on acceleration. I might have to get some kind of pressure gauge to get this checked out. At least it gives me one more place to look.
thanks to all
Well after looking at prices on convertors this might have to wait for while. Now in CO cats have to be c.a.r.b. certified which would run anywhere from 800-1300. I am sure hoping it is not the cat.

[Dead Parrot]

If that converter is the OEM pancake converter, those have a lot of back pressure even when new. Worse when they get old and carbon fouled after the magic pellets mostly quit working.

Another thing to check is the exhaust riser valve. Those can get stuck and force too much exhaust through the intake crossover. This both increases back pressure and over heats the carb, often causing a too rich condition. This can also hasten the death of the converter as it has too much unburnt fuel to deal with.

[wazzabie]

Originally Posted by truckin 79

My truck has some miles on it but runs fine except oil blow by. The crankcase filter in air cleaner gets fairly saturated. This is on the 79 350 and just wondering if there is a better system to use for oil blow by. I currently have EGR blocked off would this have any effect on blow by?
Thanks

How many miles do you think is on the motor?

[truckin 79]

Well I have the heat riser valve hooked up to constant manifold vacuum so that is one less thing to worry about. The truck has a newer convertor the old pancake one is replaced. I have seen a video that says you can take old convertor off and just let it soak in dish soap. Luckily the convertor should be pretty easy to get to and I can look to see if it is melted or just clogged. Anyone have tips on cleaning the convertor? The truck has about 160k miles on it I think somewhere around there.
Thanks

[Dead Parrot]

Originally Posted by truckin 79

Well I have the heat riser valve hooked up to constant manifold vacuum so that is one less thing to worry about. .....

If the hose goes straight from the riser pot to manifold vacuum, could explain your lack of power. The riser valve is closed under vacuum. The hose is supposed to go to one or more heat sensors on either the thermostat housing and/or the intake manifold, then back to the riser pot. The riser valve is only supposed to be closed while the motor is cold and at idle or part throttle.

If your converter is a newer honeycomb type, those should flow fairly well.

[truckin 79]

So no vacuum=stove riser is open and when vacuum is applied stove riser=closed. So If I want stove riser open all the time I should just disconnect the vacuum hose. Now I feel like a idiot

[Dead Parrot]

Originally Posted by truckin 79

So no vacuum=stove riser is open and when vacuum is applied stove riser=closed. So If I want stove riser open all the time I should just disconnect the vacuum hose. Now I feel like a idiot

Pretty sure that is how it works. My 79 Camaro had that setup and that is what I remember. But I sold that one in 2009 so have no way to verify.

I do remember that swapping a pancake converter for a honeycomb type gave about a 3 mpg improvement.

[truckin 79]

Hmmm I think you are right looking at the internet. I had a 68 Nova that had a heat riser that would stay closed until the bimetallic spring warms up and opens. I was looking at the heat risers with vacuum pods and they are open when vacuum is not applied. I guess I will unplug it and see if this is the proble, well obviously this should help with a lot of problems. There was just so many thermal vacuum switches on the 79 and I thought I was making it better.........guess not.