GMON

I know its out there but while I was doing some porting I got side tracked with this. Anyone ever tried this? How about you bigtime engine builders. I am not talking about new housings. This is for that set of housings you just cant seem to be able to throw in the scrap pile.





I noticed that the very shiny areas were much harder than the original surface areas. I assume this is becuse they have been hammerd that way from the apex seal bouncing. I would think that this would close off the pores mazda originally intended. Since I cant reproduce zillions of tiny pores I gave honing a shot.



First off I tried a 400 grit stone from an old hone I had laying arround. It would not even scratch the shiny areas. However, in the original surface it would dig in quite nicely. I used 60 grit on the shiny areas and found it took a major ammount of effort to get some lines to show up. That makes me think those pores are deafinately closed off if they even exist anymore.



Well the final product is much better than what I started with. I am sure IF i used this housing it would get much better compression than the one it was paired with that had virtually the same wear. IE no delamination yet lots of chatter and shiny areas.



I did one final experiment....2 drops of oil that were relatively the same size were dropped on the two housings above the spark plug holes. They were then set up to verticle. On the honed housing the oil spread out more than the shiny one. In fact the shiny one just kinda beaded up like a freshly waxed car and did not stick very well.



Anyway I am gonna give this housing a go......would just like to know if you guys think I am totally wacked. I kept things fairly square while i did this and really did not take much off at all. The idea was to change the surface not remove it. Again this would be for a "budget/experimental engine"



Gregory

kahren

do you have pictures of this

75 Repu

Sounds interestin... I had thought about somethin similar before.. but since I figured removing material would make the chamber bigger.. but I guess like you said.. not much was removed.. just the surface was smoothed.. it sounds like a great idea..

FikseRxSeven

from my understanding the chrome is there to keep the apex seals from wearing, now that you dnot have that shiney chrome...... i wonder how long those apex seals will last you

Lynn E. Hanover

There are many problems that can be cleared up or reduced in rotor housings.



The most common is cracking around the sparkplug holes. A close look will show that the area around the plug shows more wear that adjacent areas. The overheated plug has caused the surface to expand a bit and get very shiny.



I use a ball stone to reduce this area just enough to eliminate the apex seal from touching it. Same thing with the trailing plug hole. It can have the area where the hole intersects the surface can be enlarged slightly without penalty.



Any damage that amounts to a discontinuity that is not in contact with the apex seal can be disregarded so long as is short enough to limit gas leaking past the apex seal. So, damage that is limit to the intake area can be extensive, again so long as the surface is smooth. Once the apex seals have gathered the mix and have it in front of the plugs, say 25 to 27 BTDC then you have to get picky about damage to the surface. After TDC the pressure being contained goes way up, and tiny amounts of damage start having a much bigger affect. That makes sense right?



But even here, gas leaks will be into the preceding chamber that is open to the exhaust port.



So specifically, a deep gash in the chrome that could be 1/2" long in the intake side would not be a problem ahead of say 30 degrees BTDC. But that same deep gash in the combustion area would not be acceptable, at least for more than just driving around. OK, what does that mean?



Run out to the dumpster and get that rotor housing. Suppose that a groove have appeared that is close to or is connected to the exhaust port. That could be construed to be opening the port X number of degrees early. Well so what? You were going to do that with a die grinder anyway right?



For a beater engine (nonturbo) it will probably never show up as problem. Just be sure to smooth the surface that the apex seal touches. Sadly most failures cause damage between the plugs and the exhaust port, and is so extensive that reuse is not possible.



For those little bits of chrome that flake off in the areas between the plugs and the exhaust port, usually there as been some movement of the housing against the iron. Evidence of movement is a blackening of the aluminum. So the aluminum wears away just a bit and the chrome does not, so the unit pressure on the chrome goes way up and it fails and flakes off. That makes sense right?



You know about unit pressure, right? That is why nails are pointed on one end and flat on the other.



Anything you want to do with the chrome surface of the rotor housing can be done very quickly with a diamond file. Good tool places and gun stores have them. There are small sanding block looking files, and I have one with a fold up handle.



If you like sharp scrapers, knives or lathe tooling, you need one of these. I sharpen carbide tooling, no problem.



For flaking along the edges, remove any loose flakes and look at the rotor housing and deep into your own heart. Don't lie to yourself. Is that a big flake close to the plugs? or a small flake closer to the exhaust port? Is this a housing still good for a beater engine or a lamp project for mothers day?



You can reduce or stop flaking with your new diamond file. Drag the file around the flaking edge with the file just off of dead flat with the mating face of the housing. So if the housing is flat on a table the file would be at an angle of one degree from parallel with the table top. Just a pass to reduce the chromed part of the iron, maybe .00025" That is 1/4 of one thousandth of one inch. Or not much in plain english. The idea is to reduce the pressure on the chrome. The file cuts quickly so pay attention. Taking off too much probably won't cause a problem, but pay attention anyway. You just got this piece out of the dumpster right?



Now about those ports. A short diamond file run around the edge of ports nearly coincident with the surface will remove a microscopic amount of material around the port opening and assure that there will be no apex or side seal damage from a sharp edge left exposed.





Lynn E. Hanover

j9fd3s

new rotor housings are not shiny. its more of a matte finish.

GMON

"from my understanding the chrome is there to keep the apex seals from wearing, now that you dnot have that shiney chrome...... i wonder how long those apex seals will last you"



My whole reason for doing this is to remove that shiny part. Shiny chrome is bad and will actually cause more wear than a surface that is "slightly" rough. This is becuse it retains oil better. In a pistion this causes blow by and lower compression. I am sure it can in rotarys as well. I just wanted to verify this....



I think the reason mazda developed the pore process in the metalurgy for the housings was because it would have been harder to find a honeing process for the housings since they are not round and are very hard to measure. You need to keep in mind that stuff isn't chrome. It actually has pores in in for oil retention. Mazda spend big bux making it.



Hey Lynn, thanks for geetting all that out of your head and on this page!!!! Very helpful





Gregory

andynogo

I'd love to see what Lynn could do with a Swiss Army knife!