350 Chevy blow by

Answer 1

Blow by is caused by worn, broken or sticking rings. It's a condition where exhaust gas leaks past the piston, into the crankcase. If severe enough, sufficient pressure can build in the crankcase to push oil out the crankshaft seals, damaging the crankcase seals, or it can cause leaking at gaskets or even push oil vapor through the breather tube.
It's possible to SOMETIMES free up sticking rings by using an engine crankcase flush solution, but that only works if the piston rings are stuck in the ring groves from a history of poor maintenance. Blow by is the single most significant reason for wanting to keep your oil changed.