Hi, I have two RO Jett 67 one side ex and one rear exhaust that I am currently running. In answer to your question the person you may want to
contact is Richard Oliver. What I love about this engine is what you have noted, very steady. I like the fact that because it is actually set up to
govern speed via a muffler. You can run it faster or slower if you like. Mine runs a steady deep 4 cycle with no or very very little break
during flight. A fox 35 is a very different animal that this motor. The bar stock is there for a reason for heating and expansion purposes of
which I do not understand completely I just know it works. I also like the fact that it only uses in my case with stock venture 5.25 oz of fuel.
Frank Williams would be good one to contact also as has used this motor and is very informed regarding these things.
I am now using an Eather 3 blade 12.5x5.25 round tip prop pitched to 5.5 at our altitude 1,400 feet it likes to run in a steady deep 4 cycle at
8,400 +- rpm. I have run Yatsenko 13.4x5.9  in a different plane at 7,300 rpm +- I have used Yatsenko 13.4x5.5 also at a little more RPM.
I use Byrons 15% all synthetic Heli fuel 21 % oil to help keep the engine in the deep four cycle.This engine is set up to be very different that
the RO Jett 65 or 61 . It has a 76 Case, with 76 Crank and a modified 61 piston and liner which is thicker so as to assist with stability.
If I have my terminology correct it is undersquare not square.This is why it internally controls flight speed so well.

Please consider the above people and others as I like a certain type of run and I believe this engine is more versatile than what I am using .

  I'm reading about " Loading the engine"
then using prop pitch to adjust air speed.
That's my usual M.O. but This engine is
something completely different.

  Part of the puzzle might be the 69 oz
SV-11 is too much for the .67.

   To the last, I would be very surprised if that was true. All of these large stunt engines are extremely "powerful" compared to older engines and the rules for weights went out the window in about 1988 when people figured out how to take advantage of them.  If anything the airplane is smaller than ideal for the engine, but it will be OK at 69 ounces.

     Bearing in mind that I don't have a 67, just helped other people with them, I would suggest starting with something like 13-5 or 14-5 two-blade, or a 12.5 or 13-5 three blade, and then adjust the speed to satisfactory. If it is running way down in a 4-stroke, reduce the pitch about .2 at a time until it is running up in a fast 4 and maybe breaking in the hard corners. If it's breaking too often, increase the pitch .2 at a time until it's in a 4 most of the time. If it winds up outside the range of 4.5 to 5.5", change the venturi either larger or smaller a few drill sizes  and try again. Choose the diameter based on the airplane performance - one of the reasons I haven't tried pursuing engines like the 67, 76,  or other muffler engines is that you end up with too much diameter to make the corners clean.

   Note that you could take the same advice as above and target 4.5" of pitch, or trade off the diameter VS the pitch, and you probably should. In any case you will get a flyable system, the problem is that there are many flyable systems and you have to decide which of the many possible options is best overall. This is also why you should discount any sort of reviews, evaluation, advise from the guys who go out and fly 6 different engines in an afternoon, then pronounce judgement. Just the first step as described above might take 5 full flying sessions, and once you have 4-5 different approaches, it might take a season or two to decide which one is the best for your airplane and varying weather conditions. I got 90% of my current RO-Jett setup in about 3 months of pretty dedicated work, but we had 15 years of pre-work on other engines between three nationally competitive modelers to draw on, and I am still learning things after having tried almost everything, and come back the same setup time after time over, for 12 years.

     Brett

This is as good an opportunity as any for me to ask. Are Ro-Jett engines designed and built by Dub Jett specifically for Richard Oliver to finish with timing and porting details? Where are they made, is Dub in Japan? All this is what I have assumed, but I'd appreciate it if you guys would educate me. I'm sure there is more. It also seems I've heard another prefix besides "RO".
Thanks,
Rusty

Houston

  Correct. My mistake above.

This is as good an opportunity as any for me to ask. Are Ro-Jett engines designed and built by Dub Jett specifically for Richard Oliver to finish with timing and porting details? Where are they made, is Dub in Japan? All this is what I have assumed, but I'd appreciate it if you guys would educate me. I'm sure there is more. It also seems I've heard another prefix besides "RO".
Thanks,
Rusty

Rusty Jett Engineering is in Texas.  You can pull up the website.  These engines can be ordered directly from Dubby.  Parts and repairs also are directly with Dub. 

Dave