Hello All:

        How far back will the modern Fox .35 Stunt piston and cylinders fit the older Fox .35 engines.  I have found a new p&c and was wondering if it would fit my 1949 and 1951 Fox .35 Stunt engines.  If it is a fit, hello "new" Fox .35 Stunt engines for OTS use.


                                                                                                                                                        Tia,

                                                                                                                                                         Frank McCune

    As far as I know, the timing of the engine never changed through out the entire run, so as long as the liner is a decent fit into crank case, and the exhaust lines up properly, give it a whirl. I just wouldn't force the liner into the crank case at all. Just a slightest interference fit where it slides in and out by hand.
   Type at you later,
  Dan McEntee

   It's much more a problem with unit-to-unit variation that it is design changes, at least for any of the die-cast 6-bolt versions.

    Ideally, for iron-liner systems, the fit should be a very tight interference fit/shrink to fit, because as it heats up, the aluminum expands and loosens it up, and the heat transfer degenerates. For a Fox, it's  trade-off between the desired tight fit, and impressing the distortion of the cylinder bore in the case onto the liner. That's because the cylinder bore is cut without first heat cycling it to remove the stress, so it distorts later. And the liner itself is *extremely thin* and relatively easily distorted.

     In any case, you more-or-less have to take what you get, because unless you have a bin full of liners and crankcases to choose from, the fit you get is the one you have. There's really nothing you can do about it as an end-user, and you have no idea what will work with any particular combination anyway.

      Brett