Blue Smoke Blues

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oldjunk

oldjunk

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I have been having problems recently with blue smoke after a cold start. I do plan on doing a compression test. Here are my symptoms... Start car cold (choked/fast idle). Start to see blue smoke gradually billowing out of the tailpipes. This can be excessive at times and gradually resides after 2 minutes or so. If I kill the choke, engine will run a bit rough until warm, but cuts out on the smoke. When the engine is warm (after I take it for a spin) I see no blue smoke at all. Can run the car very hard at high rpm, let off throttle and nail it again and see no blue smoke. When warm and at idle I can pull the pcv hose at carb, plug the port and see white smoke coming out of the breather hose. Does this indicate a problem with my rings? I did recently change my pcv valve, but that did not seem to fix anything. I also recently changed my oil. I only ran the car maybe 500 miles and the oil was very black and smelled like fuel. Pulled the carb off to inspect and found what looked like oil (oil/fuel mix???) on the bottom. Car will only smoke cold, never warm or after a few hours of sitting. Tried to list every thing I have noticed since this started. Let me know what you guys think...thanks!
 
Is it possible that you are simply overchoking the thing, and or the carb is running way rich?

How about a leaking fuel pump diaphragm? If the oil appears diluted and smells like fuel, I would suspect that. THAT will not only cause oil smoke, you can set yourself up for a crankcase explosion

In my lifetime, I've been privy to THREE of those events, none of them mine.
 
Thanks for the thorough diagnostics. You are correct that "blue" smoke is oil getting mixed in with the gas.

When the choke is closed, the engine is starved for air. It's getting it from other than the intake system. That can create the situation of having gas in the oil.

Possible causes:
  1. Oil control ring worn or failed.
  2. Valve guide(s) excessively worn.
  3. Valve seal(s) cracked or broken.
If the choke were overly rich, you'd be getting black smoke.
The white smoke you are observing from the PCV hose is probably condensate being burned out of the crankcase (this is good).
 
2 Darts said:
If the choke were overly rich, you'd be getting black smoke..
Click to expand...

My thinking is that if he's using a huge amount of choke maybe it's causing oil/ gas dilution, or even washing down the cylinder walls.
 
I think yall are makin this too complicated. The choke has little to do with it, I believe. Cold start oil smoke is always what? Come on, say it with me. Bad valve stem seals and or valve guides. He said it does NOT smoke any other time. If it was a ring issue, it would smoke on hard acelleration when warm. It would smoke cold. It would smoke hot. You can run a compression test if you want, but I don't believe that is going to tell you a thing. I think it will be good. Remove the valve covers. Get a small long flat blade screwdriver and stick through a valve spring and see how soft the valve seals are. If they are hard and brittle, there's your problem.The white smoke you spoke of coming out of the hose is normal. That is crankcase vapor that normally gets pulled back into the combustion stream. Since you pulled the hose off at the carburetor, the vapor has nowhere else to go. No worries. I think all you have is worn valve seals. If it was rings it would smoke all the time.
 
If it only smokes on choke it may be emptying the bowl into the cylinders while it sits. The fuel would wash some carbon build up off the piston tops and blow it out the tail pipe. Whatever it is, it's not a bad engine. Bad engines dont stop smoking. Oil consumption wasn't mentioned either so I'll ask... How much oil are you adding between oil changes ? How much of that ( if any ) is leaked oil rather than burned oil ?
 
Well, so yall know your engine smoke colors, here they are. Gas smoke is black or grey. Water is white and oil is BLUE. You know, like when you use a weedeater? As the title says, he has BLUE smoke. This ain't as complicated as yall are makin it. Stop that. lol
 
Thanks for your input guys. This is why I love this site. I plan on taking off the valve covers and do some investigating. I sure hope it's the seals. As for the question on oil consumption, I haven't had to add any oil in between changes. You guys rock!:supz::prayer:
 
He says it doesn't smoke on a warm or hot startup makes me think it isn't the seals and is the rings or worn pistons. A hot engine will smoke for a few minutes when it leaks oil past the seals, guides. Imagine all that hot oil in the top end wanting to leak past the seals after you shut the engine down, hot. It will blow a plume of smoke and taper off. He also mentions that the oil is dirty and smells like gas. The gas in the oil can explain worn pistons and rings. Bad pistons cause more blowby..dirty oil, excess pcv fumes.. A hot and cold engine compression test with and without oil in the cylinders will only tell. Remember to use a battery charger and hold the throttle wide open to get consistent results.

What are the engine specs?
 
Once upon a time we had a '77 suberb, that suberb would smoke with cold starts and till it 'warmed up some'.
Didn't smoke under xelleration, just cold starts where it sat and enough oil could make it's way down the guides and onto/past the valves.



One day we changed the seals, and poof....no more smoke.



The only thing about this op's deal is that he has a black carb baseplate, gas stinking oil=too rich, funky timing.

Hope you didn't wash the rings out, does it feel flat on power compared to before the smoke?
 
StrokerScamp said:
I think yall are makin this too complicated. .
Click to expand...

You're probably right. The OP was talking about gas smell in the oil, I was thinking he's diluted the oil badly. That would cause oil use ALL the time, hot or cold, and probably worse hot.

Just tell me where to stick the brownie point!!!!
 
Listen to the guys, it is the valve seals. The oil collects in the top of the heads while sitting, and drains down the guides, (warm, and start it back up; it has gotten rid of the oil for a day).
 
Just re-read my reply. ok, oil drips down off the rocker assembly, down the valve stem, onto a bad seal, then down into the combustion chamber.
 
An old timer once told me if it smokes going uphill, it's the rings (high cylinder pressure, too low vacuum to pull oil through the guides) if it smoked going downhill it's the guides ( high manifold vacuum to suck oil and higher rpm than idle)
 
That's cool info. Never heard that before.
 
So I'm shopping around for the tools and parts needed to do the valve seals. Can anyone recommend a good quality overhead spring compressor or will a cheapo work just as well? I also need to know what type of seals I need for my valves. I do not have the original heads on my car. I have x-heads. Do I need to find the casting # (under the valve cover?) to get the correct seals or do all x-heads use the same seals? Also what size socket do I need to turn the motor over by hand? Thanks.
 
The simple twist-handle on the car spring compressor works fine. I use cotton rope threaded thru the spark plug hole to hold up the valves. You put it in when the piston's low in the bore, then turn the crank by hand bringing the piston to TDC. The rope pushes up on the valves and works (for me) better than an air hold. Try to make sure you get all the little peices out of theheads... Because I's had engines that sucked in a peice of old hard valve stem seal that were small enough to get past the pickup screen and they locked the oil pump up, sheard oil pump drive, and the engine was junk by the time the oil pressure was noticed and shut down.
 
When replacing the rockers, do I just tighten them down to a torque spec or is a valve lash adjustment needed. This will be my first time doing this, so bear with me.
 
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