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blue exhaust on startup


bhw33191
10-04-2008, 10:29 AM
Today when i started my car it made a blue cloud of smoke presumingly being oil. My car has never done this before, so what does it mean? I can say one thing though, my battery crapped out yesterday and i started, then turned off my car about 10 times to see how long the battery would last to assure i needed a new one. Do you think this might have to do with the cloud of smoke i saw?

Blue Bowtie
10-04-2008, 11:39 AM
A bit of oil smoke on cold startup is not unusual on SBC engines. The original valve stem seals quickly harden and don't actually offer a lot of sealing. There is usually very little oil consumed, and it isn't enough to foul spark plugs nor damage the catalytic converter. I'd be surprised if you'll even see a change in oil level between changes due to leaking valve stem seals.

In other words, if the oil is due to leaking valve stem seals, it's not actually a a problem, but merely a nuisance in some cases. It's also a sign that oil is actually reaching the valves and that burning provides a little extra upper cylinder lubrication on cold starts.

j cAT
10-04-2008, 11:47 AM
other causes would be the oil is not draining back into the sump quick enough...head drain holes gooped up, and the valve guides need work, as these engines have a problem here...as manufactured..


If this continues remove the valve cover and inspect for sludge...

bhw33191
10-04-2008, 08:54 PM
Yeah it hasnt done it since it last did this morning so i think it was just from starting it 10 times one after the other when i was messing with my battery.

silicon212
10-05-2008, 10:24 PM
That puff of smoke is nothing to worry about. Do worry about it if it doesn't stop smoking for several seconds after the engine is started.

As Blue Bowtie stated, valve stem seal leakage most often causes that puff, it's common on an older engine that uses O-ring seals like the Chevy engines, and will not cause more than a 1-2 tablespoon per 1k mile increase in oil consumption.

If the engine only puffs for a second or so, then you won't have to worry about it being anything other than a hardened O-ring stem seal. If the drainback hole in the head plugged, it would smoke a lot more than that.

bobss396
10-06-2008, 09:36 AM
You probably had it loaded up from turning it off and on. Personally, I don't trust a small block Chevy that doesn't emit a puff of smoke now and then.

Bob

bhw33191
10-06-2008, 02:48 PM
You probably had it loaded up from turning it off and on. Personally, I don't trust a small block Chevy that doesn't emit a puff of smoke now and then.

Bob

Haha. good to know

gatoratoy227
10-07-2008, 07:15 PM
its very common to see an older SBC smoke a tiny on start up even if its not every time you start it

older o-ring seals are garbage if you have the disire to do so if the smoke bothers you remove the heads and have them rebuilt

but a little oil in the cylinders isn't a bad thing
upper cylinder lube hicker-billy style

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