what is blow-by?
what is blow-by?
This term comes up every once in a while in different forums and I dont know what it means...
Gas from inside the combustion chamber sneaking past the rings into the crankcase. Where the gas is actually blowing by I dunno. Where did that term come from?
Take the oil filler cap off and watch the gas fly by. It looks like smoke. Mine varies depending on the operating tempo and the amount of boost.
A good check is to unscrew the oil filler cap, and let the cap just sit while the engine is idling. Inevitably gasses will pass by the cap, and make it move a little bit. If it bounces the cap off the valve cover, then you have some SERIOUS blow-by. If it chills, you can chill.
How does it make its way to the valve cover, through oil passages and stuff?
Blowby is also water steaming off and other chemicals being evaporated from hot oil.
Compression/Boost is lost past the rings on the compression stroke. It goes into the crankcase and raises up through the oil drain back passages to escape out of the valve cover hole. It is easiest if you leave the oil fill cap and take off the breather tube. While the engine is running you can cap the hole for a few seconds and when you release you will hear a whoooosh of air pressure.