Tommy B

So if a car puffs a little smoke on start up, but then doesn't smoke again afeter it's warm, what does that mean?

I know without leakdown #s it's hard to tell, but how bad is it to drive a car like that?

If i didn't mind the little puff, but it meant i got the car at a better price, would i HAVE to rebuild the top end?

No offense to anyone here, but i think this board is on the extreme side of how perfect their cars have to be.

If the leakdown numbers are bad, at what point is it noticable to the driver?

DGaunt

horizontal engines tend to puff on startup, especially if they havent been run for a while. IF that is the only thing apparent, it is not a deal breaker, but get the leakdown and anytinhg else you can think of to ensure the car is in good shape. That having been said, valve guide wear is critical in these engines because the guide is the main path for cooling the valve, esp. the exhaust. As tolerances climb, the valve gets hotter and hotter.

g-50cab

I think more important is to monitor oil consumption. When it gets to 500 miles or less - or you start fouling plugs, then you have a problem.

r911

if it is really worn guides then you may not pass emissions, and could have the valve burn (lack of heat xfer to guide so it heats up). The potential is that it can break drop down into the combustion chamber...

But do not worry about startup at all.

911Dave

The clearances in a 911 engine go slightly out of tolerance when the engine is cold, which allows a small amount of oil to seep into the cylinders. The puff of smoke you see is that oil being burned off and is normal. Don't be concerned unless it also does it upon acceleration/deceleration or with a warm engine.

chuck bernstein

My 87 911 cab gives off a white puff of smoke when it is first started after it has sat. Is this the good color? THanks Chuck

gr8fl4porsche

White smoke = condensation
Blue smoke = oil
Black smoke = too rich fuel mixture

Telling the difference between white and blue can be difficult.
If the smoke dissapates quickly then it is usually condensation.
If it lingers then it is probably oil burning.

If you have ever started a cold 2-stroke engine in the garage with the doors closed than you know what oil smoke looks and tastes like

ebsalem

If you pull hard up to say 5k rpm and then let off the throtle all the way and there's a puff of black smoke that's value guides. As the suction in the combustion chamber from the suddenly closed throtle tries to suck oil through the worn guides.

Steve Weiner-Rennsport Systems

Hi:

I think Jeremy is pretty well right on.

When oil consumption gets high,.....500-600 miles per qt, its time do a valve job and replace the guides with something better than the factory ones,....

Remember, the exhaust valves are amongst the hottest running parts of the engine and they are primarily cooled by how well they fit inside the guide bores. When the guides become worn, they do not cool well at all and this really raises the valve head temperatures.

In the 2.7 days (74-77), we saw many engines that dropped exhaust valve heads into the engine with catastrophic results after the guides wore out and valves failed from over temperature.

Certainly those days are gone but it simply serves to represent what can happen if worn out guides are ignored.