Small Power engine's

I like small but powerfull engines's mostly because they also are high rpm blocks most of the time, that makes an awesome sound.
So i was currious and want to know how other automation fans do this job.
Here some limitations for the engine's in this topic:
maximum size 400x400x550
minimum hp 500
maximum cc2000
minimum rpm 7500
maximum weight 150kg
And as a topic starter i added my little bee. Small but stings at 8000rpm with a max of 10000rpm with 630 hp.
This while stil beeing small and light enough and just a small 1431cc.
So i was currious and want to know how other automation fans do this job.
Here some limitations for the engine's in this topic:
maximum size 400x400x550
minimum hp 500
maximum cc2000
minimum rpm 7500
maximum weight 150kg
And as a topic starter i added my little bee. Small but stings at 8000rpm with a max of 10000rpm with 630 hp.
This while stil beeing small and light enough and just a small 1431cc.