Here is another engine that can be used for DIY model cars or teach science and engineering concepts. The TOYAN FS-L200W 2-Cylinder 4-Stroke Engine Model has an extended crankshaft to be matched for forward/reverse gearboxes. It has a max speed of 16000RPM.
This engine has an adjustable belt pulley. It has a lightweight design, making it ideal for 1/8 to 1/14 scale cars.