ORIGINAL: N1EDM
I have both engines, and I like them both a lot. I think that it depends on your intended use.
I had a Norvel .074 in a TT Scooter, and it was way too much engine for the plane. Throttling back the engine didn't produce satisfactory results. The Scooter is a lazy flyer and doesn't need much power. I took the Norvel out and put the GP-07 in.
I'm only saying that if you need the power, get the Norvel. If you are flying a lightly loaded plane that just wants to bore holes in the sky, get the GP-07.
Just my $.02
Bob
This exactly parallels my experience with the two engines. If you don't need the power as for an old-timer or other slow flying, floater type engine the TT .07 is probabaly the best bet. It is also far easier to breal in than the Norvel .074 and has the advantage of a conventional glow plug. For pure power, however the Norvel .074 is the way to go. I have had no problems with any Norvel . I think I have eight of them.
jess