My first "big" control line engine was one of these...a .29...it went into a Goldberg "Shoestring Stunter" and I still have it. ( got it for Christmas in '72 from a chain department store)

The rod is un-bushed, so you should run it on a fuel with mostly or all castor oil content. I wouldn't use more than 10% nitro either...5% should be enough...especially if you're just gonna bench run it.

My .29 ran well...but like S-P said, hot starts were difficult at best.