w ceramic seals the chrome does not wear. the only what the housing suffer is shrinking in width on the combustion side, and cracks forming around the plug holes. I think if you would run a low temp thernostat it could reduce the speed at which both propagate. In the old day people ran no thermostat and the thermal cycling more then likely didnt help.

 

as far as i know all of the MFR housings have the water seal in them, like the 1967-1985 and Rx8 engines
not sure about longevity, you will see old housings get like a "scaling" of the chrome surface

i would imagine these would be the 4801-10-100 part number, which is probably the most common one
i'm also not sure what apex seal you'd want to use, basically anything they sold was for carbon seals

its pretty cool though!

 

With no liner I would think only the softer carbon apex seals should be used.
Ceramics have less friction, but I think they're harder and designed to work with the steel lining in a housing.

 

Used ceramics for few seasons on them. No wear at all after 25-30 hours 9000 rpm shifts on the chrome.

only as I mentioned they develop cracks around the plugs and slow but steady shrink in width around the plugs

from a tribological aspect theyre superior to factory housings as the cracked surface keeps oil in it much better then the ones w steel liner. Its a bit like a sputter type bearing

 

These ports are giving me MAJOR feelings of inadequacy. LOL

 

Is there a way to prevent cracking around the plugs? Lower combustion temperatures and coolant temps?

 

I radius the edge of the plug holes

 

I would think one could prolong the run time before cracks propogate with radius/polishing the plug hole, trying to limit rotor housing temps and limiting the speed of thermal swings of the rotor housings.

Possible means to do so-
Tuning with very capable ignition system and specialized expansion scavenging exhaust (can you run richer afrs with same power?).
Cooling grooves cut in water jacket on combustion side.
Coldest plugs that stay lit.
Copper threaded insert for spark plugs.
Retain T-stat for slower thermal cycling.

Might be easier to develop a way to repair cracked rotor housings?

 

In later years certain builders made better output numbers with smaller port openings at the inner rotor housing surface. My understanding is they were tapered down smoothly from the larger intake runner size.
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yes we run the denso IW34’s in the last years. They do collect some laquer from the caster oil but still can get a full season out of a set and they are pretty damn cheap also.

 

or since they have no liner, its just aluminum with the chrome sprayed on it, maybe we can cast our own.
i suggested billet housings to Elliot at turblown like 15 years ago, but if you did billet rotor housings the billet was more money than just buying an REW housing from Mazda.

 

Unless you want a period correct racecar I would also just start from a production housing. Ideally a gsle one that is most suited to run without exhaust sleeve.

 

https://www.rx7club.com/se-rx-7-foru.../#post12582627
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Thanks for all the information, folks. Maybe I'll just sell the housings I came across. Since I already have a peripheral port but no spare engine, I was going to build one with these housings. However, if longevity is an issue (my car is street driven), then I probably won't want to use the MFR housings.

 

I know a guy in Italy that might want them. he has 2 13G engines

 

I have always wondered if machining the plug seat deeper to move the plug closer to the housing surface would help. I don't know, I'm sure it's where it is for a reason, it just seems weird.

 

looking over some of that list, a bachelors degree in voodoo might be more appropriate.
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