'73-earlier were 5mm (6mm?) one-piece carbon-aluminum seals and had two sets of side seals. '74-85 were 3mm two-piece iron seals and 1mm side seals. '86-02 were 2mm 3-piece iron seals and thinner side seals. '03-end were the short height 2mm 2-piece seals (and weird wedge shaped side seals)

This goes for all engines. The '73-earlier 10A and 12A were the same type, the '74-85 12A and 13B were the same type, the '86-02 13B and 20B were the same type.

Enough significant changes were made for '74 that they called the single distributor 12A a "12B" in internal documents, but for some reason they kept the 12A name in production. There WAS a 13A, but it shared no major components with the 10A/12A - it had a larger eccentricity and the same 70mm width as a 12A, so I ***-ume that it used the same apex seals as a twin distributor 12A.

 

12As were 3 mm. so were the 13Bs. starting in 1986, the 13B moved to 2 mm apexes.

also in '86, they started with 3-piece apex seals (as peejay alluded to above). i don't know exactly when the 3-piece seals got phased out, but i think it was sometime during the early REW engines.

EDIT: i started writing this response before peejay posted his last one.

 

The Rotary engine factory is a separate building, and its skipped all the Skyaktive remodeling and retooling. So Mazda still makes a lot of stuff, not just the Rx8

rotary history is quirky like that, right now we can get engine parts more easily than ever before because there was no new rotary car, and no plant retooling....

 

Mazdatrix has '74-78 12A rotors listed!

I thought they stopped making 3 piece apex seals when they ramped up RX-8 production. It took a while for the 3 piece seals to run out of inventory and get superseded by the 2 piece ones.

 

With only 2 major engine designs you would think that it would be easy to know what Mazda did when and how; you think it'd be a few simple iterations... WRONG!! All you professors of rotaralogy keep taking me to school!

Gents, there's been a development with my junkyard 13B... IT'S TOAST! it seems that part of the coolant gallery in the front iron actually broke away, blowing out the inner coolant seal ring in the process and completely ruining the engine. The entirety of the inside of the keg was rusty. I've yet to take the pieces to Garagelife to get seen by an expert, but I'm pretty sure they're FUBAR. The attached pics will show the extent of the damage. It seems all I'll be able to save are the tension bolts, the stat gears and maybe the E-shaft. I also made the idiotic mistake of dropping the engine off of the stand (just don't ask) and straight onto the rear of the E-shaft so that may be bent now.

The other development is I've picker up a set of 12A irons that have already been bridgeported! I know at this point I'm hijacking my own thread, but what do y'all think is a better idea? building a BP 12A or using those same 12A parts and trying to build a 4-port SE style 13B with RX8 internals. Mind ya'll that I have all the 12A parts already but no 13B rotating assembly;y and it'll be a race motor.

Lastly any thoughts on the 74-85 (and RX8) paling of the coolant seals in the housings Vs. the 86-02 placing of the coolant seals in the irons?

 

Here are some pics of the damage as I found it.

The offending iron.

A closer view of the portion that failed

How the less damaged iron looked with rotor.

Oil/coolant gunk in the coolant passage

Rotor housing damage

 

sorry to hear about your woes.

at the risk of getting your hopes up, i would say take a closer look at the rotors. the rust, in and of itself, is not a reason to toss them. many times they can be cleaned up. what you should look out for is pitting on the combustion surfaces, and even then, it depends because i have seen imperfections that remind of "pitting" on rotors that i have cleaned up, that were never rusted. personally, i have never seen rust affect the seal slots, which is not me saying it's impossible. i just have not seen it. i would say give them to your engine guy and see what he says. same thing with the shaft. let your engine guy check it out and decide if it can be used or not. you may still be on a path to your 13B after all.

i've always preferred working with the older engines, with the seals in the rotor housings. the first reason is the absolute feeling of nausea i used to get when building the Gen 2 engines. when i got to the part when i had to stack the intermediate housing, with all the different movements needed (the shaft, the dowels, etc.) i always feared the water seals would move and i wouldn't be the wiser. i eventually started using Hylomar (actually i think i use the Permatex equivalent ), and with time i got less and less neurotic, but it still concerns me even today. the other reason i didn't care for them is just what happened with your engine, where the side housing fails the seal. that said, i don't dislike them. i actually grew to prefer them for their advantages.

i have yet to build an MSP (Renesis), but i suspect i will be more comfortable with it, like i was with the older engines.

 

+1 those rotors will probably clean up. step 1 is to get the seals out, if you get the seals out, just run this rotating assembly with your BP irons and GSL-SE housings. simples

 

i started a spreadsheet, and even though the new cars are easier, there still are more variations than you'd expect. there are differences between the US and Japan, and then a/t vs m/t etc. it just gets more complex as you go back in time too

 

Despite being very pessimistic about it all given the rusty state of things, I haven't thrown anything away yet. I've boxed it all up in Costco crates and I will take it to Garagelife before I discard anything. The fewer parts I have to buy the better!! I'd gladly run this rotating assembly if I'm able, even if only until it's time to upgrade to the RX8, higher-compression rotors I desire. It'll be a little while until I'm able to get the stuff to the engine expert, but I'll let y'all know what the plans are when they're made. Thanks very much for all the help so far! God knows I'll need more soon enough!

 

That is the normal failure mode of FC engines.

 

Well that really is a bummer! I'm all but completely convinced to build an SE style 13B!