At least on the ones I have, yes, they are iron/steel. You can always do the magnet test!

All,
    I had one of these I bought from a gentleman in my area - it seems to have low compression in comparison to another one I just recently bought on ebay. Are these steel iron type piston and liner?

The reason I ask is that I'm thinking of trying the heat the piston and refit trick that has been described as brining back the compression on some of the older engines.

Will this work or am I off my rocker.

I did this heat the piston to 500 degrees in the oven and let it cool on an old fox 29 and it definitely improved the compression of this old engine. 

 

Hi
They are steel/cast iron, I doubt very seriously if you ever  will get any growth out of baking an old  OS piston, To start with they have very little growth in them when new, and any left will be  out as the piston runs hot for the entire time it has flown the airplane.
I have perssonall tried the oven trick on dozens of OS pistons. I have never had a single one improve on compression.
You would have much better luck getting the sleeve chromed then refitting the piston
Adding to this the very important thing you want to check is the wrist pin boss, most all of the  old pistons have this part of the piston worn out.

Regards

Randy

Thanks guys,
    I'll just run it the way it is until it won't run anymore then trade it in on something that will

Next question now is what newer version muffler will fit this engine - I'm going to try the LA25, and fox 35 muffers to see if they'll fit

 

Hi I have mufflers that fit the 30 and 35 S but if you want it bolt on, you will need to drill the 2 holes inside the exhaust (that the jet stream style muffler)bolted up to. Then you just put the bolts in thru the opposite side like you would a FP of FOX
If you don't do this you will need to use a strap

Randy

Or...

You could run 28%-29% castor fuel to build up a varnish layer, like most well-run Fox 35s develop...

As I recall, the .35S piston/cylinder will turn that .30S into a .35S, so the Bri-Stunt approach should be a good thing. It comes with a new rod and wristpin, too, but I think you'd need a .35 head.

The downside is that the price tag is very close to that of a new Brodak .40, which has a decent muffler, so net cost is less, power better, and parts more available. Starting may be a bit trickier, tho. Randy has 'em, at least I think I just got one from him last week (haven't had time to open the crate!).  Steve