Remixed from Pablo065's model. I haven't touched the original but I felt it needed an engine so found a suitable 9-cylinder radial online, rescaled it and stuck it in. It's a Piaggio Stella rather than the Bristol Mercury in the prototype but if you can spot the difference, you certainly know your engines. It is 9-cylinders though and prints up nicely in resin at 1:200.

Sources:

Gloster Gladiator (Pablo065): https://www.thingiverse.com/thing:4606232 Piaggio Stella (Vladimir Kafka): https://www.printables.com/en/model/67703-piaggio-stella-pix