Daniel, the rpm range that Fox claims with a 10x6 in the standard Fox.35 is 9600. Myself and all the Philly Fliers that run the standard iron piston engine use Powermaster GMA fuels. Running on the bench  with a 9x6 for break in, were turning 11800 and above. None of us are using the newer ceramic engines so I can't comment on that. If we don't generally see those rpm's we take the engine apart and perform a little black magic voodoo on them until we see those numbers.  The claims however are that the newer engine is not only lighter, but also slightly more powerful. You made no mention of the prop your swinging so it's hard to base judgment here. I have a older wide bypass Fox.35 here that has no bells and whistles other than some modifications to the crank which sustains 13800 with a 9x6 Master Airscrew on a regular basis. I will enjoy it until it hand grenades which doesn't seem to be any time soon. Ken

                      One thing is for certain Daniel , I certainly wouldn't run it hard. Fox doesn't do the plating on the ceramic engines. When they were first listed on their site, they didn't become available for several months. I was given a lot of details as to why they weren't available. These piston sleeves were made and then sent in lots to the plater. These could take quite a while to get them finished. The cost to make them was rather high and this is also a reflection of the cost. In my opinion, I personally doubt that many of these will continued to be offered. The cost vs the demand for these engines kind of puts the squash on it. I just think they're neat engines and certainly would like owning one myself. Ken

Daniel,
You didn't indicate what you are planning to use the engine for - stunt, combat, racing? For stunt on a 10x6 on 60' lines around 9000 rpm gets you at around a 4.8 sec lap time which is a good starting point. The Ceramic and ABC should break from 4 to 2 cycle a little quicker which should help in wind. For racing it should restart hot better and run stronger at the higher 10K plus rpm's they run. You can also drop the oil to 25% and get good runs.

Best,          DennisT

It is incomprehensible to me to spend about $200.00 or a little more with an upgraded head for a Fox 35. I've never been bashful on my views on the engine but we all have our opinions. Still with better engines available I haven't looked back at the Fox for a long time. But I do have 3 ABC Fox 35's and while they are smoother then stock they don't have any more power. ken said what they really need is to be freed up and I'm in complete agreement with that statement. For my money I'd rather have a Brodak 40 at $109.95. Cheaper, better runs and no burps and $100 dollars cheaper

Dennis

Well guys, I have no intention of defending the old Fox. I just ENJOY fiddling with them, running them, smelling them and hearing them.
We could say the same thing for Harley-Davidson bikes. Everyone knows they are the worst bike on the earth, but why do people buy them? For the same reason people like old fox's 35s, Old chevy's and old VW bugs. They are just plain fun to own and work on (and ride). They mean something to the person who purchased them.

I have lots of OS, ENYA and B40 engines that are WAY better than the fox. I like these engines also. Heck, I like all engines!!

'53 chevy wasn't a popular car. But ask anyone about comparing their 55-57 chevy with their current Nissan leaf, or volt, or corrola or... I think you get the idea.

-Daniel

I don't run Foxes. I run Towers and FPs. Why. Working with them long enough I can make them do what I want. Stunt. Sport. Big FPs, small Fps. (Towers are only 40s.) I also run LA46s. Do this they'll run fast, do that I can slow them down. All "modern" engines available cheap as ABC or ABN, which is generally a better way to go, then cast iron piston on steel. Better compression fit. Over lean run. So what. Iron on steel, more likely to suffer. In the Philly Fliers I am surrounded by folks who run Fox 35s. Ken among the devoted. They fly FPs, LAs. PAs, Coxes, Enyas, combat engines with names that slip out of my over 65 brain soon as I hear them. Four strokes had their vogue. Dan Banjok's into Dynajets and everything else. Diesels. Also. Plus. Who know what will be there on a given day when the weather's good or not real bad. Why do these guys keep a fair number of Foxes going on different planes anyway. It has baffled me for quite a while. Besides I get to see up close how these relics from 1949 often need some work to lap the piston/sleeve or overcome some sloppily machined front bushing. Lately Dan's been machining bushings and fitting them. So. Why use these stunt/sport dinosaurs when cheap alternatives are around. Cheap engines made of superior materials. Engines that are manufactured to more consistent tolerances. I think I am beginning to get it. One thing. They work. Get them fitted decently and they will run fast. Like Ken said. Turn a 9/6  near 14 grand. They will 2/4. They will stunt, obviously. Look good and sound apt in any old time bird while effectively pulling the plane through the pattern. Foxes are light. A stock Oriental won't need tail weight. Most sport planes fly well when powered by Foxes. They are versatile. Foxberg racers scream. Sort of. Slow combat planes can work powered by Fox 35s. Run consistently when you've divined their idiosyncrasies. They're also cheap. Real cheap. If you don't go in for the doodads.

Amazing what can be accomplished with skill and a well balanced and sharp hatchet, isn't it?

Maybe an error?

Daniel,

Congratulations on getting the Super Fox! It's common to see AAC P&L, hemi head and a stuffer backplate. They are all known upgrades that improve performance and durability but that does not make a Fox 35 a Super Fox 35! What folk don't realize is how important it is to get a straight, strong crankshaft. When Randy Smith came out with Hight Zoot crankshaft, he found the last missing piece of  the "Fox 35 puzzle". You now own the best Fox there is!

When it comes to running your "Cadillac" properly, others have already mentioned 22% oil is appropriate. What I haven't seen mentioned is amount of nitro. It needs to be 15%. Yes, you read it right: 15% nitro. Larry Forster, the person behind the RSM's Fox35 magic motors, has strongly recommended 15% and he was right! The motor runs superbly on 15%!!!!!!

Steve

P.S. The only "upgrade" I had on my Super Foxes was a special NVA made by Randy Smith for Fox 35s. Most upgrade stock NVA to a ST NVA which restricts the venturi too much. Randy's NVA's are top notch PA style NVA's with a narrow neck which does not restrict the airflow.

I seldom run Fox 35 motors. Once in a while in small planes. But that said I watch two guys at my field who use Fox 35's all the time in there Noblers go through pattern after pattern with perfect motor runs and wonder why I bother with so called better motors. Then there is the guy who never has anything quite correct and has problems all the time. "Must be the junky Fox motor" he says. He has the same problem with all his motors no mater the brand.
Ed

I seldom run Fox 35 motors. Once in a while in small planes. But that said I watch two guys at my field who use Fox 35's all the time in there Noblers go through pattern after pattern with perfect motor runs and wonder why I bother with so called better motors. Then there is the guy who never has anything quite correct and has problems all the time. "Must be the junky Fox motor" he says. He has the same problem with all his motors no mater the brand.
Ed

  There's no doubt that this happens. I also have seen, over and over again, people go out with Foxes (and other engines, too) have all sorts of issues, and then come off the circle saying how great they are. Particularly burping Foxes on profiles, someone will have the engine almost quit on an outside corner, barely avoid a crash, and then spend the next 1/2 hour gassing on about how great their engine runs.

    Brett

There is no 'Fox Burp' when you turn them up and not have them so slobbery rich that they are only half running, but hey, back in the day, thats how we ran everything, course we were not competing in contests. Lean em out and letem turn, I still prefer that kind of run, but then, I don't fly competition.     Phil

I have to agree with that Dennis. I have restored a lot of old spark ignition motors, McCoy Red Head 29's, 35's, 40's, and enjoy running them all along with Fox 35's. Not because they are state of the art, but because they are not. I rode an 84 Harley Sportster for 23 years just because it was fun. I think that is what people do not understand about the Foxes. There are certainly way better engines for doing the job, but many of us started out with them and still like their run characteristics. Way back when I had a black and white Ford Crownvictoria, and I would love to have another one. We all do similar things for different reasons. I do have to admit I am an engine guy, and there are things about the old ones that just grab me, where the modern stuff just gives me no thrill at all. As us Harley guys say, "if I have to explain it to you, you won't understand."

where the modern stuff just gives me no thrill at all.

I don't know. PA75 on a pipe got cajones! And the sound.....I get goosebumps from the sounds it makes. RoJett65 has a sound so raspy....

Then there is the "in-between" era of ST46 and ST60. Power may not have been there but the sound, THE SOUND!!!

Steve, few motors can take so much fuel. A fox 35 burns about 3.5oz per flight. 20 gallons will get you over 700 flights. I doubt you can find a ball bearing motor that can last so long.

I will grant you that if you use the right fuel and don't miss the needle,  a Fox is reasonably durable.  I had far more than 20 gallons through one of them and its still fine (or at least it was the last time I ran it in 1980).  But why do you say you don't think a ball-bearing motor can go for 700 flights? That's nothing.

    Brett

I will grant you that if you use the right fuel and don't miss the needle,  a Fox is reasonably durable.  I had far more than 20 gallons through one of them and its still fine (or at least it was the last time I ran it in 1980).  But why do you say you don't think a ball-bearing motor can go for 700 flights? That's nothing.

    Brett

I've got an Irvine .36 with over 160 hours of RC flight.  Only the rod's bottom end is showing much wear.

I will grant you that if you use the right fuel and don't miss the needle,  a Fox is reasonably durable.  I had far more than 20 gallons through one of them and its still fine (or at least it was the last time I ran it in 1980).  But why do you say you don't think a ball-bearing motor can go for 700 flights? That's nothing.

A high quality motor, properly operated AND maintained will last a long time. Fox's are not known for being of utmost quality nor ability to last. It has been 30 years since you ran one. What about your other Foxes? Were they ALL working perfectly for you over 700 flights? Were they bone stock?

A high quality motor, properly operated AND maintained will last a long time. Fox's are not known for being of utmost quality nor ability to last. It has been 30 years since you ran one. What about your other Foxes? Were they ALL working perfectly for you over 700 flights? Were they bone stock?

   Yes to 1 and 3. They did not run perfectly all the time, particularly when I started. I started out with them on a profile model, so of course there were many failures and near-disasters from the burp, since there was no cure for it at the time. When I switched to Nobler, I still had some problems  that I eventually traced to the tank design. I switched to a Sullivan round tank (one of the few that actually fit in the narrow fuse). That pretty much fixed my run issues and after than I had excellent reliability and repeatability.

    When I started running them there was no such thing as an aftermarket Fox part and modified engines of any type in a stunt plane were extremely rare. The only parts that were not the actual original pieces that came the box were then needle and spraybar, since I had destroyed so many of them from burps (and then later I discovered the business with the clocking of the flats with the threads) I had a *huge* number of flights on one of the engines, at one point I had something like 40 fuel jugs lined up against the basement wall. At 4 oz/flight that's 1200+ flights, and that was not all the fuel I had run.

   I am no apologist for Fox (or anything else), but the Fox 35 is pretty durable when you can hit the needle reliably. And one thing it rarely does is just suddenly change the way it runs, which was the thing that drove us crazy with the ST46. If a Fox is running right, it will run right until something else changes. If it's running wrong, it will run wrong (and the same way wrong) until something else changes. This led to the corollary theory that said "if it's right, don't touch it!"

    I may have misunderstood your comment - I thought you were saying (well, you actually said) that it was rare to have a ball-bearing engine go for 700 flights, which was generally a favorable comment about the Fox reliability.

    Brett

p.s. I admit I missed the "AND maintained" part. As far as I can tell there is nothing to maintain on a stunt engine, replace the plug occasionally maybe, but there's no routine maintenance required as far as I know. It *might* help to devarnish some AAC engines from time to time but I haven't and usually I get stuff to work. You just shove fuel in it and flip. That's not to say that you sometimes want to change it for performance reasons, but not just to keep it going.

    BTW. unless you run the Fox on the recommended 5% fuel, there is some chance that you will break the crankshaft (with the likelihood rising sharply if you go over 15%), but run per the directions in stunt trim even the crankshaft is durable enough.

    I am aware that there have been some durability issues on Foxes used in racing events (that's why Marvin Denny invented the stuffer backplate), but not in stunt. 

Regarding Fox durability, Duke told me of a test he ran. He got a 55 gallon drum of fuel and ran one engine all day, every day until the drum was empty. He gave up the test at that point.

Cox did a similar test on a Tee Dee .049. At 400 hours, it needed an electric starter, but would still run.

My take on this is that with adequate oil, cooling and needle setting, only dirt will wear out an engine.

The biggest thing that wears them out is running on the ground, sucking up sand dirt debris..

Randy

Hey Jim,
Don't say you are giving up control line? That would be a dreadful thing to do!

Regards,

Andrew.

Hey Jim; That is a fun thing to do. I fly an old Playboy with a sparker, and a Lanzo Bomber with a sparker both R/C. Nice change of pace from control line. And you can sit in a chair to fly. I have some back problems and somedays just do not want to fly control line, so I fly without the pain.