That is unfortunate, but might not be a death blow, from the sounds of it.
Background: !2A parts like the rotor housings are no longer available from MAzda. I am sure there are some stashed away someplace, but, finding them is elusive, at best. There are some running 'junkyard' motors, or old street motors around as well, though those are scarce as well.
So, from the sounds of it, you sucked in a water seal. Now, this, in and of itself, might not be disastrous. They can suck a rubber seal and do no little or no harm.
You can really only tell after you take it apart and inspect though.
Once you get it apart, look for damage to the housing and the sideplates. ("irons", they call them.) if everything is smooth, you have a good base to start a rebuild. A quick guide to determining condition is the fingernail test. If the depressions and wear marks on the sideplates catch your fingernail, it's not good. If they don't, get yourself a rotary shop manual and read up, and read the tolerances. To do it properly, you should have a dial gauge and so forth. As you disassemble, mark everything as to it's location.
Once you have sound sideplates and housings, get the gasket kit from Mazdaspeed. They are about $1000 or so. They'll include the apex seals, all the other gaskets and seals you'll need to assemble the engine. Also get Hylomar (I think thats the name) and vasoline. Read up on the appropriate tolerances in Mazdaspeeds online tech section.
Then assemble. It's painstaking work, and a little nerve wracking of course, the first time, but it's not impossible for a competent mechanic to handle.
If the sideplates are worn excessively, they can be "Blanchard ground" but it's not something you do at home with a belt sander! If the housings are worn, ugg. You're screwed, LOL.
using an existing running motor in a race setting is a gamble at best. 1, it's likely old, and a couple dozen runs to 7 or 8K will do in the weak seals pretty surely. and 2- it might have weak apex seals, worn apex seals or other internals that, if lunched on track will likely eat up the housings on their way out. And since housings are NLA, doing that screws you. Better to rebuild an unknown motor right up front, than destroy any chances of a rebuild by running it. The housings are just to rare to risk.
I rebuilt my motor myself, and it's gone on to lots of wins and track records up and down the east coast...and lasted many seasons.....and folks who know me will likely tell you that I'm not a F1 level mechanic by a long shot. IOW, if I can do it, it can't be THAT hard, LOL.
There are some good Rotary mechanics on this forum that have forgotten more about it than my total sum of knowledge though, like Steve Eckeridge, and a few other guys, and hopefully they can come and clear up anything I might have gotten wrong and add other points.
Hope that helps.
