Project79RX7

I'm hoping someone might be able to answer a few "rookie" questions I have. I'm rebuilding a freinds '79 RX7 (with a 12A motor) and I've come across a strange situation with this motor......and to add to the fun, I'm a newbie when it comes to rotary engines.

The problem is that the motor sat (completely still) for about 16 years....and wasn't driven all that much prior...it only has 37,000 miles on it. About 3 months ago a "mechanic" got the engine running and my buddy drove the thing 1200 miles. When they first got it running, suposedly it ran fine.....maybe a little weak on power. 1200 miles later the thing is burning some serious oil.......and blowing enough blue smoke to asphixiate a small village. So.....we took the motor out and broke it down. And, what we found was that the side rotor housings had corroded (see attached pic....it's typ[ical of all 3). The 1200 miles manange to clean most of the corosion off, but you can still see a light sheen of 'rust' on the side housings (hard to see in the pics, but the surface is pitted ever so slightly....not even measurable). So obviously, the housings need to be resurfaced in some way.....and probably replacing the side seals too.

I measured everything up this evening....and the only thing that was remotely out of tolerance was the outter side rotor oil seals. The allowable wear is suposed to be 0.5mm and these measured 0.7mm. Other than that, everything else was well within acceptable tolerances. The runout on the side housing irons wasn't even 0.001" (I know, I'm mixing units) and allowble is 0.004". But, I've still got to deal with this 'coorsosion on the side housings.

Any advice as to what I should do?


knowing that the surface runout is within tolerances,could the corrosion could be taken off with lapping only? Is it a good idea to just lap the surface?...or is getting it ground more of a requirement?

Is lapping something a reasonably skilled person could do? I can lap valves, but this looks a bit more involved. Is there a kit? or should I take it to a pro? And if so, who?

Is grinding a side housing something any reputable machine shop can do, or do I need to find someone who specializes in rotary motors?

If I have the side housings ground.....and the motor is now that much shorter......isn't the length of the eccentric shaft a concern? Seems to me I'd need an undersized thrust bearing to keep the shaft in it's proper place...but this "thing" uses a roller bearing....what do I do for those

Any help is appreciated. Iv'e rebuild my share of engines......but those all had metal parts being thrown back and forth. ....none of this spinning stuff.

trochoid

iTrader: (6)

Best bet is to send the irons out for lapping and possible re-nitriding. Lapping is generally not considered a diy project. Rotary specialist for the lapping, Racing Beat or Rotary Shack are a couple of places. Be sure to thoroughly inspect all the irons and housings for corrosion that may compromise the cooling passages, coolant o-ring grooves and lands.

Replace the oil control o-rings and carriers, corner seals (solid), side, corner (3rd gen style) and apex seal springs. The side seals can be turned upside down and reused.

After the irons are lapped, you will need a different spacer for the endplay, they come in several thicknesses. Fyi, they are torrington bearings, not roller.

Welcome to the world or 'Hmmm, the rotary goes round and round'.