Puff of blue smoke on start up: questions

I have a 304, likely high mileage. It had sat for a number of years (about 10), and just recently was brought back to life.

For the first week or so of driving there was no blue smoke. Now I notice that when I start it up I get a small puff of blue smoke. The blue smoke goes away immedeatly. There's no loss of power.

This happens when it's warm, and has been shut off for as little as 10 minutes. Doesn't happen every time.

I know it could be any number of things. Most likely rings or valve seals iirc (normal causes).

My inclination is to simply run it as is, until something actually goes wrong. Just keep feeding it oil as needed (I haven't noticed it consuming too much, haven't used it long enought to track it well yet).

Bottom line, how worried should I be? Should I investigate the actual cause, and if so what should I check first?

Other question: I like to downshift and use compression to slow down (ok, I admit that I just like the sound of that). Should I avoid doing that since it puffs blue smoke on start up? (i.e. does it put more pressure on the rings/valve seals so I should avoid it).

 

Sounds like worn valve guides.
Nothing too serious.
When then engine is off a little bit of oil drips into the combustion chamber.
When you fire up the engine it burns off and you see the puff.
You could certainly have it fixed, but its nothing urgent.
I'm sure others more educated in engine repair will weigh in.
But thats my experience.

 

It has been my experience over the years that a small amount of smoke on startup is coming from a valve seal rather than rings.

If it was mine, I would just watch the oil consumption and see what happens. I never worried about the puff on startup until the usage got to be excessive. If it was a high mileage small block Chevy and it didn't smoke a little, I would think something was wrong with it!

Hutch

 

sounds like valve seals to me,an easy fix with a few tools,well special tools, you can replace them without ever pulling the head,kd or lisel tool co,makes a fitting that screws into the sparkplug hole in the head,and you hook up the air compressor to it,with yhr rocker removed,you simply use a valve spring compressor and remove the valve spring,and replace the seal,the compressed air in the cylinder holds the valve closed while the spring is removed,this is a valve spring compressor that is intended for the springs to be removed without removing the head,no big deal though,keep an eye on the oil level,an old mechenic<since passed away>told me that and engine that used very little oil would outlast a engine that used no oil,simply because it was getting a little extra lube in places that one that used no oil wouldnt

 

Another way to hold the valves closed while you remove the springs is to pull the spark plug and feed some 1/4 inch rope in the cylinder and turn the engine over by hand until the piston presses the rope against the head.

Kind of old school, but worked great for me.


Personely, I wouldn't stress about it too much, pretty common on older engines.

 

I agree-definately valve seals. I wouldn't worry till it becomes excessive or constant. A little on start-up is fine. Just as a side note, alot of drag racers don't run valve seals and if you notice them crank up at the track their cars puff a little blue smoke untill the car warms up and enough expansion occurs to seal the valves. An old machinist told me that good valve job doesn't even require valve seals.

 

drive it till it drops....

 

If you change them. See if umbrella valve seals are available.