Office of Steam Forum for Model & Toy Steam Gas & Hot Air Engines

MODEL ENTHUSIASTS sell an adaptor if you need to buy one,  £7.99 with freepost  - extract from their website as follows :-

Run your Mamod engine from a foot pump or with compressed air
For testing your engine prior to steaming
This adapter fits into the water level plug hole (3/16 bsf)
The outer thread is the same as a car tyre thread
Provides a quick and easy way to test your engine

I have seen them listed on ebay as well. I use the type that screws into the water level plug as this means the safety valve is not removed.

Stuart