I haven't Uploaded in a while but here is something 'Excellent'. This is a hydrogen engine which should work but is quite complex. Watch the vids for details firstly the cam belt will need to be Tpu/ other flex the Cylinders will need to be sleeved with a metal ring the tops of the pistons and head will as well you will need an electrolysis Hydrogen generator the sump will need to be filled with cooking oil foam with oil on will need to be in the air filter this block can only be run for a short time as there is no water cooling this will come soon the valves need springs under then it will need RC plane spark plugs you can drill those holes in the head to suit it will need metal on the flywheel which is PERFECTLY centered (use a lathe) 8mm bars for the crank this needs M3 bolds of varing size, heat then up a bit before screwing them in and then it wil thread the holes https://www.youtube.com/watch?v=YILqOCunhB4

https://youtu.be/sWKtxron3nw

have added a water cooled block now but still watch the temp but do not use supports on this print this one has a hole for a 5mm arduino temperature sensor. i have reuploaded the inlet as it was a bit broken on the first upload i have updated the cam gears as they were the wrong ratio I have now added a ditributer and rot arm which you will have to wire up ask for advice

the build instructions should be on you tube at some point on my channel