Ask The Editors: What is Ring Gap and Does it Matter?
Not really a ring but a C.
It could be but there are many factors that can contribute to cold engine exhaust smoke – including improper valve clearances but for the sake of argument, let us assume it is the fault of the ring gap and take a closer look at what it is and why it matters.
All piston rings come as broken circles rather than complete rings. First this makes fitting them onto the piston possible and secondly the slight gap that exists once fitted serves a crucial purpose: As engine operating temperature increases, the ring material itself expands. Without a gap here to compensate for this expansion, the ring would deform and eventually fail as the engine heated.
So why then is the distance of the gap important? Too small of a gap pushes the two ends of the ring into one another. This can break the ring at the least, scratch the cylinder bore or cause a full top end failure at worse. Conversely, too large of a gap and even at full operating temperature, the two ends will remain distant from one another – making an incomplete seal. This is what would allow oil blow-by and increased exhaust smoke.
Fortunately setting up a proper gap isn’t a mysterious lost art. Piston-experts Weisco have dedicated an entire site to the subject here.
