oil smoke

[Cornpatch MO]

When I put the pedal to the metal for a little while, I get blue smoke out the tail pipes , very noticeable in the rear view mirror. Very hard to get to the plugs for a compression check , but I don't think its the rings . It runs to good to be low on compression. And, no blow by thru the two open breather caps ( no PCV valve) My Only conclusion is that it must be the valve guides. The guide seals are new and there is no smoke on start up, no matter how long the engine sits. I would like some opinions on what you think the problem most likely is..............................MO

 

[Dennis H]

I had valve guide seals fail. It would puff between shifts until they were replaced. If you repeat the exercise, does the blue smoke persist or clear for a while.

 

[Cornpatch MO]

I had valve guide seals fail. It would puff between shifts until they were replaced. If you repeat the exercise, does the blue smoke persist or clear for a while.

smokes whenever I accelerate hard, in every gear. every time. No smoke normal cruiseing @ 2500 rpm..............................MO

 

[idrivemopar]

If its not valve guides, than I would check to see if she's dumping too much fuel under hard acceleration, maybe washing down the cylinders causing the smoke, or, just curious if you have by chance installed new headers recently that are coated internally, as mind smoked for a bit after installed, thought it was something with the engine, just turned out it was the seasoning of the header coating.

 

[Cornpatch MO]

If its not valve guides, than I would check to see if she's dumping too much fuel under hard acceleration, maybe washing down the cylinders causing the smoke, or, just curious if you have by chance installed new headers recently that are coated internally, as mind smoked for a bit after installed, thought it was something with the engine, just turned out it was the seasoning of the header coating.

No headers. Can to much clearance on the valve guides cause it to burn oil? I have never had experience with guides doing that. Washing down the cylinders --personally never had experience with that, but maybe? It is a double pump 750 CFM Holley with great throttle responce- runs so good I am reluctant to mess with it.....................................MO

 

[69Runner]

Blue smoke is usually burning oil. I always thought it was failing rings under hard acceleration, and valve seals/guides under light throttle. BUT what if the oil is not draining back from the heads at the higher rpms, for whatever reason. That might explain your issue, and point to the seals/guides as the culprit.

 

[Yatzee]

When I put the pedal to the metal for a little while, I get blue smoke out the tail pipes , very noticeable in the rear view mirror. Very hard to get to the plugs for a compression check , but I don't think its the rings . It runs to good to be low on compression. And, no blow by thru the two open breather caps ( no PCV valve) My Only conclusion is that it must be the valve guides. The guide seals are new and there is no smoke on start up, no matter how long the engine sits. I would like some opinions on what you think the problem most likely is..............................MO

Your valve seals are either bad or there is too much clearance in the valve guides. The oil is sucked in during hard acceleration due to the rising vacuum created by the cylinders. I would think it would be more of an issue with the intake valve seals leaking by but in reality it's probably a combination of both intake and exhaust. A compression test will confirm the sealing ability of the rings and valves but if oil is leaking by the valve seals anyway the test would be invalid as you use a squirt of oil to verify valve leak by. Just change the seals, it's not a big job.

 

[HEMI-ITIS]

Could also be an oil leak caused by internal pressure,check and make sure your dry as a bone.

 

[69a100]

Blue smoke with the hammer down = rings.
Blue smoke when you let off the gas = seals.

 

[Shorthorse]

You're going to have to get to those plugs eventually. Along with a compression test I'd suggest a leak down test.

 

[Kern Dog]

Your valve seals are either bad or there is too much clearance in the valve guides. The oil is sucked in during hard acceleration due to the rising vacuum created by the cylinders. I would think it would be more of an issue with the intake valve seals leaking by but in reality it's probably a combination of both intake and exhaust. A compression test will confirm the sealing ability of the rings and valves but if oil is leaking by the valve seals anyway the test would be invalid as you use a squirt of oil to verify valve leak by. Just change the seals, it's not a big job.

Wrong.
Worn piston rings and scored cylinders will cause this. The engine will produce little smoke at moderate speeds. An engine operating at part throttle results in cylinders NOT seeing much pressure. The light throttle angle does not fill the cylinders much so the old piston rings have no problem sealing. This is like a slant six station wagon being UNable to break traction even with skinny tires.
NOW stomp the pedal...suddenly the cylinders are filled with air&fuel, more pressure from more combustion and all this added force puts more demand on the piston rings. Rings in good condition will seal well. Worn rings will allow oil to be drawn in from below the piston (From inside the oil pan) and that oil gets burned along with the air and fuel.
The old adage still applies:
Smoke on acceleration equals worn piston rings.
Smoke on DEcelleration or start up is valve guides or seals.

 

[Cornpatch MO]

Could also be an oil leak caused by internal pressure,check and make sure your dry as a bone.

I am not quite following you here. Where would I look for the oil leak you are referring to ? And what should be dry as a bone? Thanks..................................MO

 

[Cornpatch MO]

When I put the pedal to the metal for a little while, I get blue smoke out the tail pipes , very noticeable in the rear view mirror. Very hard to get to the plugs for a compression check , but I don't think its the rings . It runs to good to be low on compression. And, no blow by thru the two open breather caps ( no PCV valve) My Only conclusion is that it must be the valve guides. The guide seals are new and there is no smoke on start up, no matter how long the engine sits. I would like some opinions on what you think the problem most likely is..............................MO

Thanks for the informative comments. The reason I do not think it is rings, is because there is no "blow by" at the open type valve cover breathers. ( No PCV valve) I have reason to believe it could be the intake valve guides and possibly the exhaust. No symptoms of bad valve seals which were replaced.
I think the next thing is to bite the bullet and do a leak down test...BTW, just happened to think, the used short block was low mileage and cylinders did not have any scores, scratches, and no ring groove at the top. No sign of oil burning in the exhaust manifolds or combustion chambers. But I did change heads , with someone else doing the overhaul on them. hmmmm................................MO

 

[Ranger16]

There is ALWAYS some blowby. That's normal in any IC engine.
With no PCV system you are running a pressurized crankcase (and valve covers), albeit a vented one. Have you considered adding a PCV valve? Maybe running a negative pressure crankcase would help or even solve your problem. Just thinking out loud.

 

[Kern Dog]

Ricky Bobby says...."Its in the Geneva Convention, look it up."

 

[cdr]

The compression rings can still be ok, & the oil rings bad, sludged, stuck, installed wrong, the engine would still have good compression, just no oil control.