Originally Posted by fizzwater2

one option - the Evolution .46, with the one piece muffler which is currently provided, is legal in AMA 424 racing. Horizon shows it in stock:
http://www.horizonhobby.com/evolutio...ffler-evoe0461

They've been tested, and with the APC 9/6 prop, have been found to have performance similar to the TTpro .40

Otherwise, I probably have a nice used TTpro I could part with. I have several, and haven't been racing that much 424. I'd have to double check at home to be sure any of them are actually worth selling..

So far with the Evo, I haven't heard of needing to do things like replace rear bearings, etc. the Thunder Tigers, at least the earlier ones, had a bad habit of the rear bearing retainer cage coming apart and ruining an engine - most folks changed the bearings to one with a plastic ball retainer in them.