I have an Orwick 64 with steel cylinder and meehanite piston.  It has been run (lots) on gas/motor oil.  Now, compression is getting soft due to wear.

I remember comments about how castor oil will slowly plate cylinders.  Fox 35 people say that all-castor will restore compression on those engines. 

If I run this engine on the bench using glo plug and 28% all-castor oil,  about how much fuel would it take to notice any improvement?  Also, should those runs be a rich 4-cycle, or fast 2-cycle?

If it works, I would always run the engine on 25% castor oil and 75% Coleman lantern fuel (spark ignition).

I have seen engines  ruined by all castor  from the Burnt on  coke, but I have  never ever  seen a  worn out FOX 35  repaired  by running  all castor, or any other motor  for that matter

Have you tried  disassembly  and  heat cycling  the piston  to get growth?
Randy

If the engine gets overly hot the castor oil varnish will coat the sides of the piston, along with the top and bottom of the piston, and the inside and eventually the outside of the head.  It never really helps the motor run, it's sticky at motor temperatures, but some or more castor  may keep a motor running well enough to use until you can get a new piston fitted to the liner.

I have an Orwick 64 with steel cylinder and meehanite piston.  It has been run (lots) on gas/motor oil.  Now, compression is getting soft due to wear.

I remember comments about how castor oil will slowly plate cylinders.  Fox 35 people say that all-castor will restore compression on those engines. 

     I wouldn't expect that to work very well. Worn out is worn out and the kinds of clearances you are talking about are orders of magnitude looser than examples like the AAC engine thread, where it seems like varnishing gummed up the works.

     Brett

I have an Orwick 64 with steel cylinder and meehanite piston.  It has been run (lots) on gas/motor oil.  Now, compression is getting soft due to wear.

I remember comments about how castor oil will slowly plate cylinders.  Fox 35 people say that all-castor will restore compression on those engines. 

If I run this engine on the bench using glo plug and 28% all-castor oil,  about how much fuel would it take to notice any improvement?  Also, should those runs be a rich 4-cycle, or fast 2-cycle?

If it works, I would always run the engine on 25% castor oil and 75% Coleman lantern fuel (spark ignition).

Hi Floyd

Just curious, how does it run when its all warmed up & flying?  Reason I ask:  The last IC airplane I built was a Sterling Spitfire with an eBay K&B 35 Greenhead.  The engine was used but in good shape.  Ran it on Omega 10% which has something like 18% total oil, of which 3%(?) is castor the rest Klotz.  Blasphemy I know, but it worked great.  Over time it seemed to clean out some varnish and the engine kept getting better.

The engine was hard to start because of low compression - so I routinely used a starter.  At launch it ran kind of soft, it would take about 4 laps for the steel cylinder with the steel fins to heat up and (I presume) for the piston to grow out to meet it.  At that point it delivered a PERFECT 4-2-4 stunt run.

All a long and windy way of saying: I would bet your fuel runs hotter than glow fuel, and the piston fit gets better as it warms up?  Its just getting harder to start?  Never tried this myself, but I have heard of folks doing an exhaust prime with straight castor for the purpoe of trying to cheat-in some extra compression for starting...

Randy at MECOA can sell a piston/cylinder for the Cunningham Blue Streak (whenever he decides to make them).  These are supposed to fit the Orwick, but I hesitate to spend $85 for something "almost right".

   I wouldn't worry too much about the $85, this is Mecoa, you likely aren't getting it, ever.

    Brett
   

Floyd, some will grow and some do not, but it is worth a try, I just recently did two Super Cyclones and they have super compression now. I did one of my own years ago, and it still has great compression after many hours of running. It not only grows the piston but also seems to harden them to where they last for ever.

Some will grow so much you will have to lap them back in. I use Dupont #7 polishing compound or what ever polishing compound you have.

 The process is simple. Remove the wrist pin, and if you have a vise move it outside, put a pieice of music wire around and 1/8" in the vice poining straight up, Set the piston on the wire. You can just use a pair of vice grips. Get a can, like a small coffee can, and fill it at least 1 third with motor oil. I use used oil.

Take a propane torch and heat arournd the top of the piston until it begins to glow a dull red. Then dump it into the oil. If will splatter and smoke a bit. That is why you need at least a third of a can of oil.

i think what happens is the piston grows with the heat, and when you quench it so fast it does not have time to shrink back to what it was.

I have done quite a few and had almost all restor them back to better than new. However, I have yet do do an Orwick.

Another option is to talk to Dale Gleason or Frank Mcmillan as they had ringed aluminum pistons made for theirs by someone.
 
If you try the heat process I would like to know how it worked on the Orwick in case I ever have to do one. Mine has really super compression so far.

 Never tried this myself, but I have heard of folks doing an exhaust prime with straight castor for the purpoe of trying to cheat-in some extra compression for starting...
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  My best  friend had a McCoy 35 that had 0 compression back in the 60’s, when we were about 15 years old. He  brought along a can of STP oil treatment that he would put in the exhaust with a twig and then prime it with fuel. The engine would hand start with out any problem and would keep running for a full flight!
Al

Having done many, I have never had a problem with surface finish by dropping them in oil red hot. They come out smooth and round. Maybe just my dumb luck. I have run my Super Cyclone that had lost all compression for years now with no loss of compression or other problems. The front bearing is getting a little sloppy, and the rod is slightly worn, but the piston cylinder fit is perfect. So are the wrist pin bosses.

Maybe it only works for me.

Hello Jim
You are not alone in succeeding with growing your pistons as you describe, I have indeed done the same on a number of engines to good effect (especially successful was my Enya  45 (6001) and an old OS 40H that both went on to fly many flights on stunters). As I have discussed before on S/H , it did not always work, in particular on small engines like PAW's and many Fox engines . I really stuffed some that would then need new pistons and would be inclined to go the 'safe route' on more valuable engines after I ruined a valuable factory modified Oliver Tiger in the attempt (Piston split). Not sure I would want to risk a valuable and rare Orwick 64 !
Regards Gerald 

I use a propane torch, and keep it moving around the top 1/4 or 1/3 of the piston never leaving it in one spot for very long. When the part you have the torch on begins to glow dull red, I continue on around the top a little more and then dump it in the oil. Orwick pistons do have like 2% nickel. I do not know if that would be a factor. Some have already been heat treated like Madewells, and will not grow. Others like Super Cykes grow quite a bit. I have never tried any thing smaller than 60 size pistons, except for one Red Head McCoy 35 that it did not work on. They expand better by tapping the dome with a hammer to expand the top of the piston. But carefully as the sintered iron piston can crack.

I have yet to ruin a piston by heating with propane and quick cooling in oil, but that does not mean it could not happen. But, if you have a worn out engine anyway, what have you got to loose? It don't cost nothing to try. And if it does work, you will have a piston that will seem to last forever. At least that has been my experience. Your mileage may very. The Super Tech oil will clean out any carbon from running castor. Plugs stay clean forever.

I have been breaking in a couple Super Cykes that I just did, and they both have super compression where before they were OK, but not great. The one I had to do nothing but put it together, and the other one I had to lap as it was to tight. I used Turtlewax fine polishing compound for the last little bit at the top of the cyl, to leave it tight for running in. It worked extremely well. They both have good compression hot or cold. A little better cold. But start very easy either way. Usually one flip hot or cold if primed right. All my sparkers have been running on stove fuel with 25 to 30% Super Tech 2 stroke oil from Walmart. It runs very cool and does not leave a sticky mess.