the valve guides could be worn out
The carburetor is running fuel rich and needs adjustment. If it were valve guides or rings the smoke would be blue
Injectors, timing, low cylinder pressure.
Excessive revving of an engine causes overpressure in the crankcase. It causes unhealthy expansion in the pistons and the valves.
Unburned fuel in the exhaust system causes the backfire from the exhaust pipe.
Water vapour due to condensation in the exhaust pipe.
It is timed incorrectly or plug wires are installed incorrectly.
"lead" is the Pollutant from motor car exhaust that causes mental disease.
No who, but what. All internal combustion engines emit exhaust fumes.
Burning oil
Broke rings on pistons
burning oil
gas from the exhaust
Two big causes of noise pollution are vehicles (cars, trucks, car horns, revving engines, planes, ect) and loud music.