Hi Dave,
My Ro-Jett 76 venturi diameter is 0.202-0.205".
I have received this black, nylon venturi with my engine from Dub Jett and never touched it.
I will use this venturi, unmodified, to break the engine with a 12x5 two-blade Master Airscrew and 5% nitro, 22% fully synthetic KLOTZ oil and will report the results on this forum.
I know that Ro-Jett76 is a low RPM, high torque engine.
The take-off RPM for flying the Pattern I am aiming for is the 7,000 -7,500 RPM range with 13 x 6.3, 13.4 x 6, and/or 14.2 x 6 wooden CNC propellers from Ukraine.
Thank you for your suggestions and opinions,
Regards,
M