OK its been a while, the waiting is over!
A package made it to the house today and I even found a little time to look at
the rotor housings.
This is a very quick check and at first glance they are perfect,
the width is within spec and the bore is very close, but I have yet to check the bore with a bore gauge.

Here is what I did measure.
You can see in these pictures what I found you can make your own conclusions.
I am posting what I see with out prejudice.

The time it took to get to this point doesn’t matter and I am sure no one getting housings done in the
future would have a delay like this.

I will say that I will be using these housings with nrs ceramic seals so they are close enough for
me to feel comfortable using them. After all the apex seals are over 1000 and I wouldn’t chance using
them in a housings I didn’t feel good about.

would I recommend getting housings done at jhb?
YES
would I get more housings done in the future?
YES

matt

 

What results do you expect, now that you have them back.

 

Why do choose to put the ceramics in though?
It would seem that you would prove them with stock seals then throw those ceramic seals in once t has proven to work well only changing 1 parameter, and knowing that a investment like that would be safe and sound?

Other than the time involved with tearing it down, it would seem practical to do so, and you strike me as a person that doesn’t mind taking a little extra time to be sure of something.

Good luck regardless!
How many miles do you typically see in a year?

 

They look great Matt...

 

why ceramics?
JHB suggests the use of ceramics with their housings.
also this motor is being built for a guy who wants it pinned and clearanced as well
as thermal barrier coatings on the rotors. (something I am doing myself now)
it will be run at 12 to 15 psi boost.
the last engine was run at the same boost numbers and needed to be rebuilt due to a side seal failure.
this time almost everything is now and should be reliable to 15 psi or more.
matt

 

they are not perfect but are much better than before
I really would have like to see "0" on the dial gauge all the way across the
surface but 2 thou shouldn't be enough to worry about.
matt

 

Silly question.. (not being critical, just seeking clarification.) I can't see the rest of your measuring jig. What reference point is the other end of your dial resting on? At first glance it looks like you have both the housing and dial base resting on a table. Is the base located by the dowel or something?

Edit--- Nevermind. After looking at the pics again I see what you were measuring. For some reason I thought you were trying to compare two different housings. Still, with this measuting technique, you're relying on the fact that the bottom of the housing is perfectly flat and exactly 90° to the housing. Since this is a surface made to be sealed with glue, I wonder if this is acceptible.

 

the housing is on the carriage of my lathe and the dial gauge is on the bed.
i checked the carriage with the gauge before and it is a solid "0" all the way across.
matt

 

You need to clamp the rotor housing to a precision ground angle plate, sitting on a surface plate, and taking the measurement with an indicator attached to a surface gage. This will tell you whats up.

 

for a quick measurement of flat what i have done is within .5 thou
a stock mazda housing in new condition i can get a "0" all the way across which is
what i would call perfectly flat.
the jhb housings with a slight drop off at the edges of a couple thou is close enough
it would have been nice to see perfect but i guess this is as good as it gets.
matt

 

more pics dude and you better show us some pics of the assembly with those

 

very very cool Now 2 thou out is not horrbily bad but it can be better, what would be your recomendations for Apex seals for a daily driver but a friday night racer Rx-7?

another qeustion for ya, where in Alberta do ya live?


Prôdigy

 

I thought these housings were ground via a machine so as to have no variance? What are mazda's tolerance on this?

Thanks for the update as I have a few housings eventually that will need this treatment

Are you going to check to see how much material has been added. (for Rotor clearance?)

From what I can see the look good. Alot better then used ones

 

I would use the mazda 2 piece seals they seem to be the next best thing.
I am in wetaskiwin (just south of edmonton)
later
matt

 

A new mazda housing is almost perfectly flat, they are all a little different
but are all very close to spec.
this falling off at the edges is due to deflection IMO .
I have yet to check the bore to see what the clearance will be like but will for sure
check rotor clearance.
matt

 

Hi Matt, have you made any more measurements of the housings? Interested to see how "thick" the coating is

 

well there is no real way to measure how thick the coating is other than to drill a hole through it in a number of places, i dont think i realy want to do that
as for more measurements i have not really had time been to busy working on the garage.
matt

 

If you make the back half of the engine you should be able to measure the gap between the apex of the rotor and the housing. This should be exactly the same all the way round. This is what went wrong with the ones Tim got.

 

or stack a new mazda housing on top of the resurfaced one with the dowel pins in them
and they should be the same.
they appear to be really close, maybe a thou or two out which is close enough.
but will look closer and will be clearancing the rotors before it goes together.
later
matt

 

For anyone who is wondering, Ceremet is a hybrid material. It's a cross between ceramic and carbide; being harder than carbide but more impact resistant than ceramic. It's an amazing coating, and the Ceremet A coating is identical to the coating used in the 1991 LeMans winner 787b.

Ceremet is most commonly used in the tooling industry as a material to make thousands of cuts for manufacturing steel parts.

 

What's the difference between Cermet A & Cermet B?
The JHB website doesn't go into detail other than that Cermet A is twice the price.

Kyle

 

Bump.
Anyone else use them or have any findings?

 

I'm using them in my halfbridge FD engine, and also a few customer FC engines at this point. All used with atkins or mazda seals. THey build a strong motor just like new mazda rotorhousings, with great initial compression (100-105psi after 30 minutes runtime) and great compression later (I am currently seeing 115+psi with 600 hard breakin miles on my engine with 3mm seals and solid corners). I can't comment on the power increase due to lower friction, but personally comparing them to stock housings they are certainly harder and slicker. The coating is so hard that it is in fact very hard to port compared to a stock housing.

My second big batch of housings is on it's way from JHB now. I plan to keep this as an option offering for my rebuilds for a long time.

 

hurry up and get that motor together so we can get more feedback. although, i love what i'm hearing so far.

 

porting should be done before housings are sent off to be coated.
the stuff chips off if you are not careful.
matt