Excuse the back track here but...is this the BB version of the 61 or the standard Ro-Jett timing version? The higher timed BB version will probably have "BB" or "BB Timing" inscribed somewhere on the case if it is (or at least the ones I have seen do). Not sure if the BB setup will work for a standard timed Ro-Jett. 
It's a much better starting point than the "chart" method, because that's how we started, and we have actually run them that way in real life.
The RO-Jett 136-degree version runs a lot more like a PA (since the exhaust timing is the same) than the 140 or 144 version. It actually runs more like a PA61 with the Aussie crank timing modification - because all but the earliest engines run the same crank timing as a QM40 pylon racing engine that is also very close to the VF.
I ran 17.5 on the PA61 as well, and with the Eather pipe Dave and Ted were around 17.75 - but check the pipe tuning article. The slightly extended pipe (compared what you would expect by comparing the duration) reduces the boost/brake a bit to improve the run quality and reduce the tendency to overdo the response. This was all with launch revs in the range of 10,000 or so and pitch around 3.75 to 3.9, and in-flight revs around 10800-11000.
The RO-Jett barstock version, at least, is not prone to a tendency to break into a hard 2-stroke on outsides. The cast-case version, interestingly, *does* seem to have a bit of that, not as bad as the PA61 and nowhere near as bad as the PA40, but it does have that tendency. We were watching Jim Tichy fly his RO-Jett barstock engine up at Napa, and when he got to the square 8, Ted and I both listened for the usual screaming fast outsides, and nothing, just like the 46VF. I was looking around for a cell phone before he got to the 4-leaf because we had never been able to solve it completely on the PA. The later versions of the PA seemed to be a lot better in that regard, and David more-or-less has solved it for the PA75, mostly by finally getting a large enough engine that it can be detuned enough to stay afar away from the break point.
The PA51 never seemed to have the issue to any great degree - probably because of the extended intake duration (almost the same as the 40/46VF) because Brian Eather and Paul Walker both got great improvement by matching the PA51 intake timing. The crank timing modification may have gone a bit too far, because it replicated the PA51 in another way - it tended to start backwards and was able to run fast that way!
There's a lot more to it than just looking at the exhaust duration. In any case, I think you are always better running something that is already proven than starting from scratch with theories. The RO-Jett 61 is clearly the best stunt engine I have ever run, even better than the 40VF.
Brett
Topic: Ro-jett 61 prop advice / changed to pipe set up (Read 13036 times)