Backfire through oil breather....

[p24-1953]

  tonight i was adjusting my idle speed on the 230 and noticed that when reved some times i get a Back fire and it kinda sounds like it is coming  from the driver side or the bottom end.  Could it be backfiring from the oil breather? Or the down draft tube. It does not do this when driving in gear. Nor does it do it every time.  I checked the oil and it looks fine and does not smell like gas.  Any thoughts?  What could cause this?

[BigDaddyO]

https://en.wikipedia.org/wiki/Back-fire

[torqczar]

  backfire should come out of exhaust.  BOOM !  if it is, look for distributor  problem ... if combustion is happening in pan, you would have many other problems  .  so my guess is  valve not seating  [ sticking  valve or  valve guides worn] ,    lean mixture  [ accelerator pump ,vacuum leak]   , retarded timing   [  dist. timing , worn timing chain ],  in that order.   not enough info to diagnosis  properly.  

[ptwothree]

If the backfire is during acceleration, it's a timing or fuel or intake valve problem and will go pow in the intake manifold/carb area.  If popping is heard while the engine is decelerating, it is usually caused by an exhaust leak.