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Engine basics => Engine set up tips => Topic started by: bob whitney on August 17, 2016, 08:20:50 PM

Title: Fox 35 stunt hole in piston
Post by: bob whitney on August 17, 2016, 08:20:50 PM

  ok, I have a good one  /just received an almost new fox 35 stunt with Hemi head and stuffer backplate ,he was breaking it in with 35 %oil and a 10/5 prop.the piston has the ex side of the piston crown gone .nothing but a big hole. has anyone ever heard of anything like this

Title: Re: Fox 35 stunt hole in piston
Post by: Howard Rush on August 17, 2016, 11:13:59 PM

The Mark 3 Combat Specials' piston tops would cave in after awhile.   

Title: Re: Fox 35 stunt hole in piston
Post by: RandySmith on August 18, 2016, 10:58:27 AM

Quote from: bob whitney on August 17, 2016, 08:20:50 PM

  ok, I have a good one  /just received an almost new fox 35 stunt with Hemi head and stuffer backplate ,he was breaking it in with 35 %oil and a 10/5 prop.the piston has the ex side of the piston crown gone .nothing but a big hole. has anyone ever heard of anything like this

Any marks on the head button inside?  I have seen people crack the exhaust side by not having the button install  perfectly straight, then they fail when running.

Randy

Title: Re: Fox 35 stunt hole in piston
Post by: frank mccune on August 18, 2016, 12:22:34 PM

     Hello Bob:

     A club member gave me a Fox 15X that had a large hole burned through the center of the piston. He claimed it was from too much nitro in the fuel???????

    How long would an engine have to run to do that much damage and how could it run long enough to remove that much metal?  The hole was about 2/3 the size of the bore!

                                                                                                                              Frank McCune

Title: Re: Fox 35 stunt hole in piston
Post by: Steve Helmick on August 18, 2016, 01:22:46 PM

One extra lean run with enough nitro and/or compression will work wonders. The correct amount of nitro changes with each engine. Some don't require "a lot" to do the trick! LL~ Steve

Title: Re: Fox 35 stunt hole in piston
Post by: kenneth cook on August 18, 2016, 02:37:35 PM

           Nothing indexes the Fox .35 hemi head button. If it wasn't aligned properly to the piston when assembled,  the baffle could've  struck the head and caused the damage as you mention. There's not a whole lot of room for error either.

Title: Re: Fox 35 stunt hole in piston
Post by: Russell Shaffer on August 18, 2016, 05:05:41 PM

Is there scrap metal in the crankcase or is the piece clear gone?  I bet the head button did have something to do with this. 

Title: Re: Fox 35 stunt hole in piston
Post by: bob whitney on August 18, 2016, 09:15:15 PM

 
 the baffle is still intact ,the broken pieces were still in the engine. I cant see any marks on the piston, head or cyl . the engine had three or 4 tanks run through it before it happened

Title: Re: Fox 35 stunt hole in piston
Post by: RandySmith on August 18, 2016, 09:43:44 PM

Quote from: bob whitney on August 18, 2016, 09:15:15 PM

 
 the baffle is still intact ,the broken pieces were still in the engine. I cant see any marks on the piston, head or cyl . the engine had three or 4 tanks run through it before it happened

As I stated  early  the head  can be broken by putting the head on wrong then it will break when you run it, you may not see any damage to the baffle

Randy