Looks like it might be a 33cc, though we won't ever be sure until you measure it. Here's some info I found for that casting number:

http://www.powermowersales.com/pages...2f0625230005~1

Funny, I was thinking if it wasn't a Poulan that it probably was a Homelite.... I think I have one like it in my stack of engines, but I've been too sick to go out and search for it in the shop.

Note that the above info doesn't guarantee that it is a 33cc, because I believe that crankcase bottom with that casting number will fit more than one engine. You need to go ahead and measure your engine. But in any case, it will make a good airplane engine. The larger engines, found in backpack leaf blowers, chain saws, etc. have better ports, better port timing, better carb sizing, and considerably more power than the weedeater and small blower engines. You'll like it for sure, whatever size it turns out to be.

AV8TOR