This is a mystery to me, I wonder if any kind people here, can help explain whats really going on. This 350 runs perfect, does not smoke or burn oil, the exhaust pipe was coco brown when I bought it. I then changed the oil maybe 4 times in about 2 years 6k miles, try to flush it out. Now it smokes, but only when at idle for extended periods of time. If I start it up and drive it and stop at a traffic light, thats fine it does not smoke. If I start it up in the morning and let it idle for extended period of time it smokes. If on the freeway and run into road construction, then idle for long period of time, after say 5 min, then it starts to smoke. Then road clears up and within a mile or so, no more smoke. Just looking for ideas on what others think is causing it. I think I changed the oil often and knocked sludge loose and blocking the return oil ports. Now it is overflowing into the chambers and burning at idle. Is that even possible? Thinking maybe add some seafoam to the oil and change it again. This motor with a manual transmission is a kick in the pants to drive. Will run 90 mph down the freeway all day long and not burn a drop of oil. Let it idle for 5 min and starts smoking.
I do not have the tool to do a leak down, can do compression. I will need to make it up. In the past, my old sbc with a common leaking valve guide problem, would puff out smoke when they sat over night and start up. This motor does not puff out smoke when first started, only smokes after extended idle.
Pull the valve covers and see if there is goop &gunk clogging up the oil return passages in the heads. at idle you have high vacuum you could be sucking oil thru a PCV . or maybe a intake manifold gasket?
Possible the intake, I did not think of that ... the pcv valve does shake rattle and roll, and I sprayed some cleaner in it. Just trying to eliminate the pcv from the equation, it seems to be fine. Going to replace it though. Once I posted this thread, I then read it and thought ... pull a valve cover and find out. This motor/trans/rear gear really puts a smile on your face. I was told it had 50k on the motor. But is old and been sitting. Just trying to get some ideas before taking it apart. Trying to understand what is going on with it.
I second the high vacuum sucking oil in somewhere... Maybe you could block of all the vacuum ports as an experiment?
Pcv stuck Plumbed in wrong Intake manifold leak Vacuum leak I’m not thinking rings, valves or guides as it’s not smoking constant or when cold , cold starts is usually when you see oil burning with worn guides or seals.
It's not likely to be plugged oil return passages. There is a lot more oil moving when you're running "90 mph down the freeway all day long" than there is at idle. If return passages were plugged you'd be starving the bottom end after a couple minutes of running 90 mph because all the oil would be stuck under the valve covers.
This is what I kinda think but not sure. It is a newer engine in a older vehicle, the intake has been changed. Just because the pcv works, does not mean they installed it correctly ... I have to check this. And of course the manifold leak, I would think this to be like a vacuum leak. Affect the tune of the engine. I honestly would drive this engine anywhere and not want to touch the tune of it. The idle is perfect, the response is perfect, gas mileage sucks, I would not change a thing.
If you can find out the year of the engine What valve covers where on it new ( vented, non vented) What type of pcv system it came with from factory Fueli engine converted to carb Egr engine? Cheap n dirty Cap and or remove all vacuum stuff Get an oil catch can like the dragsters and tuner folks use and get rid of your pcv set up and report back. Google and YouTube oil catch cams lots of homemade stuff you can do for basically 0 dollars.
Just for fun......"smoke" or lack there of comes in many colors....... What we talking here? White/Black?/Blue? Plz elaborate...
Does you engine just have the O ring style seals some times the metal shields that go between the springs and retainers are left off. the shields really help with oil control at the valve stem. https://images.search.yahoo.com/sea...es/g/zv0AAOSwjqVZHKOR/s-l300.jpg&action=click
How much oil is it going through? If it is burning that much oil every time it warms up you have to be adding oil on an all too regular basis and you haven't said a thing about how much you have to add. Smoke at an idle when stopped in traffic could mean a carb that is running far too rich just as well as burning oil. Especially if it acts up and runs rough. The oil burning probably wouldn't have as much effect on the way it idled.
A PCV is a vacuum leak. its a metered leak. you tune your carb to compensate for it. a intake leaking you could also have the engine tuned to compensate. Ive seen improperly baffled PCV,s that sucked oil. Ive seen engines that had broken rings run great and only blow blue smoke under certain conditions. Pull your PCV how much blow by does your engine have? On a chevy V8 If its very much at all you need at the very least new rings.
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