The Stovebolt Site Forums The Shop Area Engine Shop We have a couple ideas for fixing the white smoke

First off its not completely white after all, i took a closer look. When it comes out the pipe bunched up it looks white, but when it separates and expands, it gets a very very faint blue color, like oil. The truck has been driven a good 25 miles already and the smoke is still pouring out. It doesn't begin right at startup though. I can start the engine in neutral and run it for 30 minutes without any smoke whatsoever. However, if i barely tap the gas pedal and let off (it still being in neutral of course) the smoke starts to pour and it will do so until i shut it off. We took it to a guy just to precisely tune the valve clearances and had to drive on the interstate. The looks of the truck get enough attention, the smoke just made everyone honk at me. I'm going to go pick it up tomorrow after school. By the way, does a hollow pushrod mean hydraulic lifters? Because we thought they were at first, and tightened the rockers till no play, then 3/4 turn more. Gas started shooting out of my carburetor when i turned the ignition. BUT, when we thought they might have been solid and did clearance to .0015", it started right up. I thought clearances were for solid lifters? Anyhow, lets get to the point, or shall i say points. Wow, sorry that im writing a novel guys. When we get the truck back, im going to check the sparkplugs as blackjack mentioned to see if they have oil on them. Next, i want to run a compression test, so if somebody wouldnt mind, I need to know what the compression should be for a 250 L6. But what we think is the culprit behind all this is.....drumroll..... The PCV Valve! Before we started this project, one end of the PCV hose came out of the valve cover, but the other end just hung loose next to the engine, not attached to the intake like we have it now. Also, the valve cover grommet for the PCV valve is all worn down (Popping the valve in the grommet is like throwing a pencil down a mineshaft), i dont know what condition the valve itself is in, but im sure it's bad. We think thats it. Any advice and opinions will be greatly appreciated. Again thanks everyone for their help through this 2 month long project, She runs, we just have to fix this problem and I'll be on the road for good.

You might be on the right track as a bum PCV valve will do exactly what you are describing.

White smoke associated with a blown head gasket and burning antifreeze is truly 'white' and behaves like steam when coming out of the exhaust pipe..it just disappears into thin air. Smoke from burning oil will have some faint blue tinge, but won't disappear like coolant smoke, it will hang in the air and trail for quite some time.

Stuart

Silly question...what does the smoke smell like? This can be a tell-tale sign of what is happening inside the engine.

Sounds like blowby from a faulty PCV valve. Is the motor newly rebuilt? If so the rings may not have seated yet.

Thats really odd about the valve adjustment. You might try and adjust them with the valve cover off while its running. Sometimes a lifter adjustment will hold the valves open till it runs a few seconds, so if you only cranked it, the adjustment could still be off. How does it sound?
All the 194,230,250,292's were hydralic lifter engines, so you may have a aftermarket solid lifter cam.

Something else to consider, if the valves are not adjusted right, oil will really be spraying around under the valve cover and you could just be getting to much in the PCV valve.

Does your valve cover have a deflector inside around the PCV opening?

Joe

It sounds like you are describing oil smoke. Does this truck have an automatic transmission? If so, disconnect the vacuum modulator line from the engine and see if the smoke disappears after running for a while. Plug the vacuum connection at the manifold. If the smoke clears, the vacuum modulator diaphram is leaking and needs to be changed. Memory is foggy on this, but I think the ATs in that year still used a vacuum modulator connected to the intake manifold.

I don't think the PCV valve is the cause of your trouble, even though it may be stuck open. If the valve is as loose in the grommet as you say, there wouldn't be enough suction on the crankcase to draw any oil through the PCV circuit. But you could certainly get a rough or poor idle with the valve fully open.

Decent compression pressure for your engine would be 120-150 PSI, and more or less the same pressure in all cylinders. Much above 150 would be reason to suspect carbon buildup in the combustion chambers, which could be caused by ring or valve guide leakage. Much below 120 PSI for any cylinder would be reason to suspect valve leakage, or some other cause, depending on how much variation you find. Do dry and wet compression checks and let us know what you find. Do the dry check first, then give 2-3 squirts of oil from a pump oil can and check the compression in each cylinder again. Ring leakage will show up as an increase in pressure of more than about 20 PSI.

Also, check the color of the spark plugs. Dark and dry indicates the spark plug temperature is too cold, the causes of which may be slight oil consumption, rich fuel mixture, or the spark plug heat range is too cold- wrong spark plugs. Black and crusty, either dry or wet, typically indicates oil consumption, but with several possibilities.

Let us know what you find with the compression checks and the spark plugs.

Harvester

Pouring white smoke is a good indication of water - ait freeze - cracked head - or blown gasket.

got the truck back today after he adjusted valves, it's still smoking. Sparkplugs are black and crusty. Guy that did the valves said the rings might be faulty. If that's the case then im $!@#%%#
We never miked the bore and we just bout standard rings for the pistons. We did hone it out though. The smoke clearly smells of burning oil. I'm afraid that im gonna have to get the cylinders bored out and get oversized pistons. Although i have yet to run the compression test so don't know if it's that for sure.

I don't know if I have all of your posts pertaining to this, but from what I gather you have overhauled the engine. I believe even if it had a fair amount of taper the new rings would seal up the cylinder enough to not be the problem with oil consumption. I have known professional mechanics that put rings in a motor with .030 taper. I would not do it myself, but the engine ran for a number of years without excessive oil consumption.

I would be leaning toward the PCV valve. You said previously that it was not attached to the valve cover. This was probably not by accident. I would disconnect the hose from the valve cover and vent the fumes to the atmosphere, as God had intended.

I just clicked on the link below your signature to have a look at the pictures of your truck including the pic of your engine.

You made comments about your PCV valve not being connected to a vacuum source but that the hose just went down behind your engine. You said that you now have connected it to a vacuum source at the intake ( where it should be) correct?

The picture of your engine shows you have a solid oil filler cap on the valve cover but you need a breather type cap.

Your intake vacuum hose to the pcv valve is creating a vacuum inside the engine- sucking oil into the intake.

Put a breather type oil filler cap on and see what happens.

Just for clarification, if it was my rings, shouldn't the smoke be black?

I agree with the comments about excessive taper. New rings will control the oil pretty well. Burning oil produces blue smoke. An over rich mixture produces black smoke. I would be chcking out the PCV setup.

This smoke also occured when we had the valve cover off. But maybe the rings hadn't set yet, as we had just started it. Any idea how long rings usually need to set?

I hate to be the bearer of bad news but, if people are honking at you because they think you're on fire, your oil consumption is catastophic. A PCV system that is not creating a vacuum and is plugged will only help create oil leaks. The vacuum helps keep pressure off of the seals and gaskets. I say it's in the cylinders. If the rings were doing their job, the PCV problem wouldn't be able to get the oil past them. The mention of little to no smoke at idle would indicate oil ring problem since not much oil pressure or splash is happening at idle so little oil can get by the rings. When it picks up RPM is when the oil is really moving around in the crank case and it's when the smoke comes on. The sooty plugs are a symptom of this. It wouldn't be the heads since bad guides and seals would cause smoke upon start-up.

Without actually being there though, this is just an educated guess and a proper diagnosis should be made first. A better test for this would be a cylinder leak-down test. Since the engine runs, the compression rings must be doing something, so a compression test might not tell you much,
Scott

the inside of your exhaust is now coated. Get a vented oil fill cap and run it for a while to burn out the tailpipe. It sounds like Dave64 has the answer.

Black smoke is too much fuel. Do tha compression test and then repeat but with a tablespoon or so of oil in each cyl. If the rings are bad the compression will go up with the oil in there. Shake the pcv valve, and if it rattles, it's good, but I would replace it anyway as they only cost a couple of bucks. You must have a breather to go with the pcv. Oil smoke that occurs mainly @ idle is usually from the valve guides, under open throttle is usually rings.

You said your spark plugs are black and crusty. All of them? Is the black dry and powdery, or wet and slick? I would'nt imagine all of your cyl.s having bad rings, but I guess it's possible. If you can, do a leakdown test, and you will know for sure what the problem is.

I'm guessing it's an assembly problem,
Scott

What is a leakdown test?

Before you do a whole lot of diagnostics, please disable the PCV valve and vent to the atmosphere. It is possible that there is something missing in your valve cover to keep the majority of the oil from the PCV valve. I once had a F--D truck that took an unbelievable amount of oil. I replaced the PCV valve and it didn't help. I finally just plugged the intake where the hose went from the PCV valve and vented the fumes to the atmosphere. The oil consumption went to almost nothing. I still believe something was missing in the valve cover and it was sucking way too much oil through the PCV valve. Anyway, it is fixed now with no PCV valve.

Crabby, there is a baffle that is on the inside of the valve cover that prevents oil from being directley sucked into the carb or intake from the PCV.

My dad always told me to look for the obvious and always replace the cheapest parts first. Example I had a 350 with a TH350. It was noisy like a rod was knocking. Got worse as time went on. Was about the yank the motor when a buddy said "I bet it's loose torque converter bolts" I listened to him and sure enough thats all it was.

What is the history of the truck and engine? Why was it rebuilt?

If it was using oil before, it will take some time to clean out the tail pipe. Get it out on the highway and run, coolant will also take a while to burn out.

Vent the valve cover,
change to new plugs,
check the oil real close,
drive it,
and recheck the oil and plugs.

Let us know after you do this.

Joe

A leak down test is the most definative means of checking engine condition. You place the piston near TDC, and introduce compressed air through a special set of differential gauges. One measures how much pressure goes in, and one measures how much leaks out. All motors leak some, but how much determines the condition. Also you can listen around and figure out where its leaking ( exhaust, intake, rings, etc.) If you have never done this before I would recommend having it done by a pro, as there are some hazards involved ( the engine needs to be stopped from turning, the air pressure can move the entire vehicle and wreak havoc!) Also the tester cost a bit of change ( autozone loaner maybe?)

I remember in about 1986 I put in some new rings in an engine and had a bad oil smoking problem when I got done. What I found was that one of the rings was upside down. It scrapped the oil up instead of down.

Ok, ran the truck last night, with and without the PCV valve hooked up. Only difference was i idled really high with the valve unhooked. I went to plug up the hole on the intake with my finger, and it almost pulled my arm down into the manifold, now thats suction! Anyways... IT DID NOT SMOKE. We ran it for about ten minutes and i ran it up and down the street with the valve unhooked from the intake and once with the valve hooked up to the intake. Now, i brought it back to the warehouse and my dad got in it and redlined the darn thing. Then it started smoking, but just a tad bit, not like Auschwitz as it had before. But, only way to know for sure is to run a compression test. Gonna do that today. But im wondering, just turn the starter for how long with the gauge hooked up?

Did it smoke while "redlined" or after and was on idle? If it smoked a little after the "redline" and idling, it is most likely valve guides.

On the compression test, it shouldn't take too many turns to find the higest reading. Just be sure to have the footfeed wide open. You can look at the gauge while you are cranking. It will take only a few seconds to reach your high reading.

I think you found your main oil consumption problem by disconnecting the PCV valve.

Now go out and buy a breather cap like we stated before. It would idle high different with the vacuum leak. the fact that it idled high indicates that you are running rich.

Where the heck did you have the PCV hose hooked up to? It should be plumbed into the air cleaner, NOT full manifold vacuum. You will need a vent (like a vented oil fill cap) and a baffle under the PCV valve to keep oil from entering the system. The PCV system is for keeping pressure out of the crank case but you don't want a lot of vacuum either. Seals and gaskets can get damaged from both,
Scott

Ran compression test. 3 cylinders hit 100 psi, two had 90 psi and one had 110 psi. Ran wet tests on the two 90's and they both gained 5 psi. What does this mean?

oil sealed the rings a little better...
compression should be between 10% of one another
Compression should improve as the new rings seat to the cylinders..

Any vehicles I have worked on with a PCV valve have it plumbed into manifold vacuum, with a breather or hose from the engine to the breather to allow filtered air in.

Yeah, I guess so, I've never owned a 6 without a road draft. The V-8's have there's going into the base of the carb and the vent hose going through the aircleaner. Sorry about the brain fart,
Scott

I don't really see a problem. The compression is pretty good, the smoke is mostly gone, and it runs OK. Drive it around and get some miles on it. Get it out on the highway so the exhaust gets really hot and dried out. Run it hard a few times to clean off the pistons and spark plugs. Then come back and check the timing and carburetor setting. If it still has a problem, recheck the compression. Joe

Compression will improve with breakin miles. Kinda low now, but if you can keep it running long enough it will likely be OK. Pcv goes to manifold vacuum, breather allows air in. I sounds like you're mostly out of the woods! Congrats, after this ordeal it must be a good feeling to see it turn out Ok!

You betcha it is, the past 3 nights i haven't been able to sleep cause all i could think was that i'll have to bore out the jugs! This thing has run about 40 miles since we first cranked it, how long does it take on average for most rings to seat?

A few hundred miles to get a good seat.

In my humble opinion, If your blowing that much oil, I have a hard time thinking that your rings are the problem...unless a few of them got installed up side down (even one of them), wrong size (under sized) piston rings, a broken ring, or way too large of a ring gaps. A new engine, or new rings shouldn't smoke more than a minute or two at the most on initial startup. If you change your oil after a couple hundred miles and you have burned a quart of oil, something is wrong. It just shouldn't burn that much oil.

On my IRWIPI, after building my 283, I took a 100 mile drive down some county roads. After each stop sign I slowly brought it up to 40 mph and then floored it up to 55 or 60, I did that about 10 times to break in the rings. Otherwise I took it real easy. I drove it back 100 miles down the same county roads and changed the oil when I got home. After that, I drove it like I drive anything else. Did another 500 mile oil change and after a couple of thousand miles, all is OK. I can't say I ever saw any oil clouds coming from my exhaust.