The O.S CVRX .18 will give you all the power you need. If you went to a larger engine ( other than the traxxas ones ) your gonna have to do a pretty good deal of modifying to fit a BB engine in a volcano. I know, I have the tsunami ultrawide and I've looked at other engines to upgrade to, and so far the CVRX is the one I'm mostly drawn to. The BB like .21s and .25s and larger are gonna require you to completely rearrange your entire drive train. Yes it can be done, but your gonna have to work for it. The O.S .18 CVRX should just drop in and offer more power than your stock drive train will probbably be able to handle. You will break dogbones much more often, and you'll definetly wear out your drive cups in no time and don't forget your diff gears. So, if your gonna be adding power to a volcano, make sure your ready to do the upgrades to the drive train to handle all that extra power. But it'll be fun working on it and fixing it too. So anyway that's my 2 cents.