https://www.youtube.com/watch?v=aQuToSKaLzk
how pulsejet engines works
https://www.youtube.com/watch?v=p8FSa5peEUk
https://www.youtube.com/watch?v=jEnNMTMZadw
How to make a pulse jet engine for a RC plane
https://www.youtube.com/watch?v=obFnt5KKrVc
Having a reed valve up front allows more air intake and during combustion the valve closes maximizes thrust is really the way to go. The vent or shutter type open up even more air intake increasing the volume to allow agressive fuel burn for max thrust within the realm of these types of jet engines.