Let's start with engines that we are using now, and what we think about them. Their good points and their bad points. What kind of engine would we like to have. A where we have been able to find them.

Personally there were two engines I preferred, The K & B 61 and the Picco 60. The K & B 61 was a great engine for sport flying. It was inexpensive and parts were plentiful. They still are today. It came with a Perry Carb and was the best of the day. Even though it's not a power house, it would pull a Kaos with plenty of zip.

The Picco was a powerful engine and pulled the heavier pattern planes with some gusto. The inflight fuel mixture control was a big help for tweeking a mixture right before take off. It came in both configurations as rear exhaust and side exhaust.
Others were using the Rossi, Webra and Super Tigre. All great engines.

The worst engine was the Fox Eagle 60. With the bolt on carb you were limited to just the Fox carb that came on the engine. They were big and heavy. That's my opinion. There were some guys that swore by them. Oh, and they were cheap.