Col,

you may need to put a metal spacer between the venturi and the nut. It may have "run out of thread".

For what its worth the PAW compression screw thread is 2 BA. You might have trouble getting that size in a heli-coil. You could tap 1/4" x 32 UNEF, which is the glowplug thread. Steve Rothwell has his R250 comp screws at this thread, and he sells spares for about AUD 10.

Otherwise, its a bit course but how about tapping 10-32 UNF. You can get the taps and suitable socket head screws at a good hobby shop. R/c warehouse up your way would be a good source.

Regarding the Oliver clone, it was probably a "Rustler MK3 Olly" copy. Assembled and sold by Ian Russel in the UK from high quality Russian parts.. Usually about GBP110 or so when available, but a much better proposition than a CS. I can supply contact details. Otherwise you could get one of Steve Rorhwell's R250s. Just under $400 Australian. There is a waiting list.

regards Ray