Ummmm..........that would be detonation or pre-ignition....not sure what "pre-detonating" is.

The rattle is the mixture lighting off BEFORE the actual spark......basically two ignitions on the compression stroke. (the "real spark" should be around 30-35* BTDC....in other words while the piston is still going up....the compression igniton or detonation I'm "guessing" happens 10-15* BEFORE that)

Again, study up on 4 stroke engine operation............the valves are closed for nearly 1 1/2 full revolutions. As the piston is going up to compress the mixture, valves are closed (how else could compression build?) as the mixture is ignited, the piston is forced down (again the valves must stay closed to create any downward pressure) only on the upward exhaust stroke will the exhaust valve start to open and when the exhaust is forced out at aprox TDC, the intake opens and the piston draws a fresh mixture in.

I realize the Amish aren't supposed to know this stuff........but I won't tell anyone.