I acquired a Cosmo motor to throw in my third gen temporarily until I have the three rotor plans in order and ready to execute. I wanted to experiment with the engine a bit just to see if and how well it work. I originally intended to slap it in unmodified. I became worried that it may have unseen internal problems (based on the experience of others).



Well I cracked her open today and it was mint inside. I really got lucky judging by others experiences. It was definitely a low mileage engine. Housings were perfect, side plates were mirror.



Anyway, to try and keep costs down I'm porting and assembling the motor myself. My main question is, what can I keep? I've decided to replace the apex seasl with Atkins (but I may now go back to Mazda OEM 2mm). How about the side seals? I've removed them and labeled them as per rotor and position so I can put them back where I found them. Anything else that I can keep? I'll be upgrading to a 3rd gen planetary gear while in there and upgrading to the Atkins side seal holders which are one piece and eliminate the piece of plastic in the inboard side. Anything else I should do while I'm in there? I'm actually rebuiding it at the local rotary shop and will be receiving their help in the rebuild. I'd just like to do it as inexpensively as possible without hurting reliability. TIA.

I would highly suggest replacing all the seals and their springs if you want good compression.

also the mazda factory apex seal are the best ones your gonna find. My .02

i have heard the atkins apex seals are the best!

from other people's opinion's around here i heard atkins OR mazda OEM are the way to go...depends who you ask..just dont get hurley..baddddd

straight edge, feeler gauge, torque wrench, razor blade, carb cleaner, wire brush, and scotch brite. you might as well clean everything since it's already apart. get the atkins 2pc 2mm apex seals. you can keep the springs, side seals, and that other stuff. get new inner/outer oil rings (6 inner and 6 outer), 6 outer water jackets, 6 inner water jackets, new inner/outer oil seals, new o-rings, thermal pellet, hylomar, vasoline, tap-die set, and i can't really think of anything else you'll need. the bearings, washers, and needle bearings should all be good. do the webber 200cfm oil jet mod, you can pick those up at BAP imports. that's all i use to rebuild the engines (if they're as good as you say). have fun! https://www.nopistons.com/forums/pub...#>/biggrin.png

What did the cosmo cost you?

6 inner and 6 outer oil rings?? he needs 4 inner and 4 outer oil rings. I think he has a 13B Cosmo engine not a 20B Cosmo engine..





If your going to rebuild this engine I would agree with FD3boost.... every single seal is mandatory for good compression and reliability. Atkins apex seals work, but stock Mazda 2mm seals are better. Make sure you use a nice Micro-meter and the necessary gauges and tools to mic and clearance every single part. From your engine bearings to your seal clearances to the wear on the side housings, to the width on the rotor housings, to the end-play on the flywheel.

Arghhh, Ito how do you do all that measuring.. It's enough to make your eyes pop out. https://www.nopistons.com/forums/pub...IR#>/blink.png

How do you plan on porting the stock "D" exhaust ports? Or will you replace them with FD/FC ones?

Well that's the big question....Check out the porting thread. Setzep, since you have an RE, what did you do? Isn't it possible just to remove a bunch of the material as you would with the FD's exhaust sleeves? Ito? What would you recommend?



Yes, it's a 2 rotor, not a three. Cost was $1600 with shipping.



If porting the exhaust sleeves isn't an option, I guess I'll replace them with FD sleeves. I've also heard there are some custom sleeves available out there as well but I haven't had a chance to do any searches for them yet.



I've pretty much decided to replace all the seals except for the side seals. If the side seals turn out to be inexpensive then I'll probably replace those too. There was soooo little internal wear on this engine though.