I read a number of threads regarding the TT GP 42.  General conclusion was that pretty much everyone liked it.  Opinions ranged from as good/better than a LA 46 to not as good as a LA 46, but good anyway.  Anyhow, I've acquired several.

Installing the venturies, on the first two I put in the OS FP 40 venturi, which measures about 0.282" or 0.283".  Then, reading the instruction sheet for the motor, the dang thing isn't a 42 after all, it's a 40 (0.396).  So, the question on the venturies.  As I said, the large OS venturi is about 0.283".  The FP 20-25 size I previously bought measures 0.268".  The current FP 20 size they're selling now measures 0.259". 

So which size have you guys used?  I always put the 0.268 size on the LA and FP 40 engines.

I'd appreciate your thoughts/experiences.

Thanks,

Herman

I don't have some, but Leonard Neuman wrote that the venturi boss/bore is tapered, so it takes some extra PITA to make venturi inserts fit. Have you looked into that delightful feature?  Steve

Veturie size'd depend on prop , plane size & weight , Line Length , and altitude at field .

A venturie that works at 3.000 in the mid thirties C ( about 90) does about 80 mph at sea level in the teens .