Reasons for excessive exhaust smoke?

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Tylan

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This is a recent occurrence, just started a couple start-ups ago. I'm pretty sure it's burning oil but could be wrong. The exhaust is near invisible at first, as normal, but will start getting REAL smokey within 30 seconds of running. I think it's burning oil because I changed the oil last month and the dipstick already shows a large amount gone. The smoke is also thick and gray, can see blue at night when I shine a light on it. I've heard that burning oil is commonly caused by a clogged or bad pcv valve, but as far as I know the valves are just simple check valves and mine has plenty of clearance. My other guess is the piston rings, no idea what kind of condition those or the pistons/cylinders are in. Like I said, recent occurrences, not sure if rings/pistons/cylinders can go south that quickly.
 
And clean pcv valve, check that hose isnt clogged and make sure the vent that lets air in is clean.
Also, diluted oil will burn off faster too. Make sure the oil isnt loaded up with gas, like a fuel pump leaking into pan.
 
Also could take a good look at the oil visible on the dipstick. Is it discolored? What does it smell like? Pop the radiator cap and check the coolant while you're at it. If it smells like exhaust you know what's happening.
 
Also could take a good look at the oil visible on the dipstick. Is it discolored? What does it smell like? Pop the radiator cap and check the coolant while you're at it. If it smells like exhaust you know what's happening.
That would indicate bad head gasket right?
 
I assume checking valve seals and stem seals requires me taking the engine apart...
 
If you don't have a compression gage, try turning the engine over by hand. You can do that in a slant by pulling and pushing on the fan belt at the alternator, if no shroud. It turns cw looking at the crankshaft from the front. If you can fell each cylinder strongly resist you (3 per revolution, chalk the crank damper), and you must wait >3 sec for each one to hiss down, then you have excellent compression. If true, it is likely getting oil past the valve stems. As mentioned, the rubber umbrella seals may have rotted.

Don't fear removing the valve cover, as that is a regular thing on a slant to adjust valve clearance. You can change the seals w/ engine in car, but must remove the valve springs and one at a time so you don't drop a valve out of the head (have piston at TDC). But, don't tackle that without reading up a lot and thinking it thru. Ditto for adjusting valves, though less risky.
 
When does it smoke worst? If it does it after sitting overnight or a day or two it's either bad valve stem seals and or valve guides. The bad seals and or guides allow the oil to drain into the combustion chambers slowly after sitting long periods. Then, when the engine is started, it will smoke. Sometimes badly. It's easily confirmed by removing the valve cover and looking through the valve springs at the seals. They are probably cracked and broken all to hell.
 
Yep an old seal cracks and the other side finally gives and it falls off and just sucks oil down the loose guide.

once it smokes, say ..to rule out a pcv issue... Disconnect the pcv hose n plug it then see if it still smokes.
Probably the stem seal scenario though.
 
So I removed the valve cover today, didn't see any thing immediately. The valve seals seem to be intact but I don't know how old they are, could very well be hard as rock making them useless. The only thing out of the ordinary was that cylinder 2 had a seal that was seemingly lower than all of the others.
 
I remember something like smoke on acceleration is rings and deceleration is valve guides. I think.:rolleyes:
 
Ive had several engines whose valve guide seals "look" good when removed, but oil consumption goes way down after those seals are replaced.
 
Make sure your PCV hose is not collapsing under vacuum, or freezing up. And that the breather is not iced up
I read here or in the factory service manual that a way to check the PCV is to remove the oil filler cap with the engine running and hold a piece of paper or something like a 3x5 card over (close to) the valve cover oil filler opening. If the paper is pulled the filler opening, the PCV works.
 
Even the cheapass umbrella seals are light years ahead of what was available decades ago.......as long as you don't get some NOS horse crap been layin on the shelf thirty years. You can get the stock, umbrella seals in Viton. Those are very acceptable.
 
I read here or in the factory service manual that a way to check the PCV is to remove the oil filler cap with the engine running and hold a piece of paper or something like a 3x5 card over (close to) the valve cover oil filler opening. If the paper is pulled the filler opening, the PCV works.
That proves the PCV on a fully functioning system.
But if the paper is not sucked down, does not mean the engine is shot. It just means you have more checking to do.
If the paper is not sucked down;You
may have a CC air leak somewhere else. or
there is a restriction or plug in the PCV line between the valvecover and the discharge port , or
the breather ain't breathing, or
in some cases, a wrong basegasket under the carb.

I have seen;
PCVs frozen up with ice,
lines sucked flat,
breathers plugged up,
and wrong gaskets,and
missing baffles under the PCV, AND
too much oil in the CC, or oil mixed with something else.

This last one is not common so often gets missed. When the crank is sitting in the oil and spinning, it creates a tremendous cloud of oil-mist all thru the engine. The PCV picks it up and out the tailpipe it goes as blue smoke.
 
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