blue smoke

i was wondering my car blows out a little blue smoke when I get on it. It seems like this has been happining reciently when I put my exhaust on ( i have shorty headers, an h- pipe w/o cats and flowmaster cat back) I thought it might be valve seals but my oil pressure is fine. Any imput would be greatly apriciater. Thanks
 
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Black or grey smoke = rich; the blacker, the richer

Excessive white vapor = coolant in the combustion chamber (leaking gasket or cracked component)

Blue smoke = burning oil; on acceleration usually rings; on deceleration or start up usually valve seals/guides
 
How much is it? can you actually see the smoke out the rear window when you get on it, or is it something someone else may have noticed? does it smoke at idle? how much oil are you down between changes?
 
its not that much, my friend said he saw it when he was behind me, i mean i dont see anything out my rear view mirror, but sometimes when i come to a light a little will pass by my window. it doesnt do it at idel, only when i get on it
 
How many miles are on your motor? Do you drive it really hard?

Forged interals in the 5.0L engine require more cleance between the cylinder walls / rings. Most people see a small puff of smoke when they are shifting from 6,000RPM. To me it sounds like you should start saving for rebuild...
 
The extra clearance is required because of the different rates of thermal expansion of the cast iron block and the forged alum. piston. Once the motor is warm, the cylinder should seal up pretty nicely. Unless, of course, it's just time to do something about a tired motor....

catman - how many miles on this beast?
 
Michael Yount said:
Black or grey smoke = rich; the blacker, the richer

Excessive white vapor = coolant in the combustion chamber (leaking gasket or cracked component)

Blue smoke = burning oil; on acceleration usually rings; on deceleration or start up usually valve seals/guides

What a great little nugget of knowledge... :nice: thanks. I've never heard that before. I mean I know what the smoke colors indicate, but not to that level. I never thought about accel. and decel. indicating different problems.
 
catman - you can have oil pressure that's just fine, and valve seals/guides leaking like crazy. The two things don't have to be related.

Best thing to do is have someone follow you and tell you what it's doing. You can't tell from inside the car nearly as well. Put in 2nd gear and accelerate hard from about 2000-5000 rpm, and then let off the gas (be sure the guy following knows what you're gonna do). He can tell you if it's smoking on acceleration or deceleration or both.

Cranking compression and cylinder leak down tests will confirm cylinder seal and give you more detail on where the problem exists.
 
There's a device that screws into the spark plug hole, and a source of compressed air. A set of gauges read the pressure of the source vs. the pressure the cylinder is able to maintain. A certain % drop between the two indicates how well the cylinder is holding pressure. You perform the test with the piston at TDC (unless you don't mind getting run over by the car or spinning the engine) on the compression stroke (both valves closed). If the shop/equipment (compressor remotely located) is quiet enough you can listen at various places to see where the air is leaking. Noise in the tailpipe usually means air is making it past a burnt or bent exhaust valve; noise in the intake track usually means a bent intake; noise through the oil filler (crankcase) means air leaking past the rings.

The leak down test is often performed after a cranking compression test is run on all 8 cylinders. If a particular cylinder is more than about 15% low from the rest, it's a candidate for the leakdown test.

Catman - how much oil do you add between changes? How far between quarts?