Ive made a ton of 7K passes with the 440 and street drive.My kids 300 has made probally 300 passes on the OE motor and just 2 breathers and probally 10K street hard miles.Neither has a problem.If you had gas in the oil you would know it.That or try the lighter test and see if it flames quick.Carb would have to dump a ton of gas to cause it.I say blowby.Rocky