Cox tee dee r/c 05 and tee dee r/c 09

Congratulations, beautiful engines there..
I have a couple of both...the 09-s power my Cosmic Wind and Sig Wonder RC planes. Very dependable engines but need either pressurized tank or a tank placed level or even slightly higher than the engine CL to provide enough suction.

I used the 050-s on my Toucan RC planes but finally swapped in 049 and 051 TeeDee-s with eitherTarno carb or exhaust throttle which is a way stronger setup than the muffled non-SPI 050.

My 09-s were made in the 1960-s or 70-s (crystal boxed) and came with excellent fit and tapered cylinder bore. SPI engines, not genuinely RC, but I turned them RC with either exhaust throttle or RC carb and turbo heads, so even with a muffler - that is contra-pruductive to SPI - they are very powerful.

The 050-s are younger, made only in the mid-90s with less tight cylinder fit. I prefer vintage COX engines 2 or 3 decades older than the 050-s - which I still love nevertheless- , when the hand paired piston and cylinder lent top quality even for the highest production run, mass produced product engines compared to those only 20 or 25 years old.

I also prefer longevity of compression to short lived brute power (i.e. features of the mouse race COX engines of less tight fit), hence my inclination towards tighter fit cylinders.

I have 70+ COX engines, some older and others younger, so my opinion and experience are based on a limited bunch of them..I may be wrong.