I'm running a Dirt Demon with the orig. 26 engine. Runs fine & it comes with a roto start but you have to get your own batt pack for the starter & the red push button on top needs replacing, the button just stuck on onw day so I've been using another one. The 26 has had a minor flow job on the crank, & the sleeve ports are matched to the case, about 7 tanks (20%) since new. I'm not even running the Demon right now as my other truck takes most the time, it has a 24.7 pro & comparing the 2 I'd say the 24.7 has it all over the .26 in the bottom end but the .26 has a little more top end. Unless your used to 3-needle carbs I'd say go for a 24.7 pro, for the price its hard to beat. If you want to sell your Siro post me a pic of it. I put some pics in here of both my trucks a few months back so maybe you can find them. Ones a ThunderQuake, & the other is the Demon