Why is the oil and gas mixing in your Chevy 350 engine?

If your having oil burn-off its most likely because the motor is worn out and the piston rings are allowing oil to get past into the cylinder. If you have overheated the motor it could be a cracked block or head. Some Chevy 350s, like the one in my impala, the factory head was too thin and would crack about 120k miles. Basically if your oil is getting in the cylinder there is major internal engine work that needs to be done.