Did Duke Fox write the Fox 35 Stunt 28% castor oil requirement back in the early 1950s, then never update it with the addition of synthetics?

Is Brodak control line mix of 11.5% castor/11.5% synthetic an excellent brand to run or all the fuels on the market lacking for the Fox 35 Stunt and need supplements?

I would like to tell you there is one Stunt fuel formula to run in all motors, I said I would like to tell you that…unfortunately this is not the case, and will never be as long as we have such a wide range of motors and running styles.  What I will tell you is a good formula for the most common types of engines.  Make sure you pick a fuel supplier who will give you consistent fuel day to day ,and will blend fuel for your motor needs or has fuel to match your needs.  Stay away from any supplier who will not tell you the oil percentage, or who say one type works for all motors. I see this  much to  often also, It is unfortunate, but a lot of fuel manufactures will try to fool you about the oil and nitro percentage. One trick is to measure  by weight and not volume. Doing so, they can claim that the fuel is  for example 18 % oil , when in reality it is only 14.9 % oil content. Using weight  for ingredient , they can put in a  lot less oil and nitro . Other things are changing oil types, going to cheaper Nitro’s, and adding in other types of Nitro parrafins.

   So what percentage do you try? For motors like Fox .35s, OS Max 35s or the old McCoy’s and K&B’s, use a fuel with 26 to 28% oil content; preferably half castor and half synthetic, up to 75% castor  is OK. These  motors have very small bearing surfaces, and are subject to much wear and heat, most are all plain bushing motors and most have unbushed rods. They need a lot of  oil  to help cool the engines. Since these motors run hot, they need  extra oil to keep them lubed,clean, and to carry out heat . If you have one of these that is  in very good  shape but, is  just starting to get some brown or black varnish plating on it, the synthetic mix will clean it  up for you, resulting in increased life.  Do not use the synthetic  blend in an old motor that has a lot of time on it with all castor fuels; the synthetic will remove the castor varnish off the piston and sleeve and will in some cases, leave you with the worn-out motor that had to start with.  Also always try to NOT use  prop shaft extensions with these engine, as it adds a  lot of  wear on the crankshaft bearing.

For motors with larger bushings and bushed rods like to OS FP , Magnum GP series, Tower, and  Brodak’s  a 22-25% half-and-half oil mixture works the best.  For S.T. .46 51,and .60s and most all ball bearings Stunt motors, a 23% half blend works best. Again the Synthetic blend will help keep the engine  clean, and insure long life. If you use  all castor in these  types, it can stick the ring in the groove , resulting in poor compression and  shortened engine life. If you have a ringed engine that castor has gummed up badly, most times running the synthetic blend will free the stuck ring, and the engine will  return compression and  power for you.
   The tuned pipe motors like a little more synthetic and I recommend a 15% synthetic, 7% castor blend or a  20% half and half with 1  ounce of Aero-1 fuel supplement. Although many use 1\2 – 1\2  with great success.  This works very well in the  Precision Aero , OPS and Max VF engines,  Super Tigre  Thunder Tiger, AERO TIGER and most all of these type engines..

Not exactly. Synthetic oils for fuels simply did not exist. The first synthetic oil additive to my knowledge in the late 50's was STP, which meant  Scientifically Treated Petroleum.  Andy Granatelli pushed it and we did use  it engine rebuilds in the Chevrolet dealership I worked in.
Those early engines, not just Fox, had all iron sleeves, pistons and rings and needed an oil that would get into the pores, flow towards heat and castor does this. It ain't perfect, but it works. 

     It's certainly not unique to Fox.

     Fox did experiment with synthetic oils briefly. I used to have a Fox Superfuel can with a sticker about using "new synthetic oil". It dated from the 1966-1967 time frame. It was similar to what K&B did with "X2C oil". They dropped it in pretty short order for reasons I think we can guess (and is explained in Randy's fuel post pinned at the top of the forum!).

     Brett

  How do you measure by weight versus by volume?  What formula do you use when using by weight?  I am not famiular with these uses..  Thanks a lot

The actual formula for Fox Superfuel was: (the numbers were on the label of the can )
29% AA Castor
64% Methanol
5% Nitromethane
1 % detergent (Lubricin N-1)
1% Ignitors (Propylene Oxide)
Fox used a combination of synthetic (Klotz) and castor in "Dukes Fuel" and others up until they went out of the fuel business a couple years ago. They may have produced some Superfuel with an oil blend but we never saw any of it.

      Technically, it was painted onto the can, it wasn't a separate label, so they came up with a sticker to mark it when they went to synthetic (briefly).

     Using straight castor or adding castor above 22%,  particuarly in 5% fuel, can have a remarkable effect on some Fox 35s. Going from 22% to 28% adds more power, sometimes, than going from 5% to 10% nitro. 

Both is even better - you can really perk up any Fox 35 for stunt by adding nitro in almost any quantity, but you had darn well have enough oil in it. You crankshaft life will be greatly reduced above 15% nitro, however.

      Brett