Ok, so if you are doing a rebuild and replace all the seals, gaskets and the housings, you essentially have a almost new engine. Do you not?

The rotors are not replaced, but then, they do not have any friction surfaces of their own (outside of the replaced seals. And if they and the e-shaft are well within tollerance it should not matter that they are not new.

So it seems to me that the only thing now preventing the 'new engine' smell is that the irons may be out of tollerance.

Can you machine all three irons at the same time and still have a engine assembly that is within tollerance? I haven't read anything that says no.

So, if I take out my 200K engine while it is still running and before it hand-grenades itself, and rebuild it using new housings, what is to prevent me from getting another 200K? [Assuming I do a decent rebuild job.]

 

as long as your irons/plates are in spec . as long as your eshaft is in great condition. and as long as your housings are in good condition you .
irons are rarely "lapped"
lapping is resurfacing the irons. most people clean the irons by 600 grit then 800 grit sand paper to clean the plates. the housings can not be treated this way because they are chrome plated.
housings are most commonly replaced with newer, better condition rotor housings depending on the milage of the rx7.
with 200k. i say inspect the bearing surface (the hole in the rotor and the eshaft surface) for anything at all. it needs to be as mirror as possible. no lines.
these are not to expencive to replace. but need to be done if it is not in spec.
i am not speeking from full personal experience. i am undergoing a rebuild right now and this is what i have learned in the prossess. i am not a rebuilder by any means but i am just giving out what little i have learned

 

Almost new, yes.

The main wear area for the rotors are the apex seal grooves. The seal rocks in the groove which over time wears the tips of the groove wider then the bottom. Once they are worn past spec the only thing you can do is discard them, or have the rotor machined for 3MM seals.

I don't know if I've ever seen a "worn out" e-shaft. All the bad shafts I've seen have been due to oiling problems.

The irons just need to be flat. As long as the machining does not result in an iron that's too thin, getting then flattened is not a huge deal. You can machine all the irons, one iron, one face of one iron, etc.

You might find yourself with a set of worn rotors and worn irons in addition to the regular replacement items (seals, gaskets, torrington bearings, etc.).

There's nothing to say that a rebuild won't last a long time. It's just that most rebuilds are done half-assed.

 

i took some irons to a guy that polishes mirrors for his telescopes.



um... yeah, that guy, i dont know what he did, but it was polished soo well it looked like a mirror almost. smoothest thing i ever felt.

but that was on a junk iron. o well. i need to figure out how he did it. he said he built the machine himself.

 

I've had my vert since it had 0 miles on the ODO - picked one right off the truck on Dec 13, 1988.

It is in excellent condition and getting the engine and tranny back to 'trustworthy' will prepare me for the next 19 years.

Thanks for the info.

 

I also measure rotor-to-iron clearance by subtracting the rotor width (at the gear surface) from the average rotor housing width (the 4 measurements taken per the FSM). I have mixed-and-matched rotor housings and rotors to get the clearance within spec, and have rejected a few rotors that didn't meet specs. A new housing, obviously, will be in spec.

 

You probably wouldn't want to do that for a real engine, though. Machined surfaces (cylinder walls, irons, etc) aren't perfectly smooth - they've got small ridges in them. A perfectly smooth surface won't hold oil properly, and it'll wear things out faster than a proper surface. A perfectly smooth surface is similar to a glazed cylinder wall, and things just don't work right.

-=Russ=-

 

Good point.

Plus you wouldn't want to have the housings lapped without getting them re-nitrated. I was talking to the guys down at Atkins and they were talking about how the no longer lap the irons in the "newer" engines (or something like that). Something about the nitrate process has been changed and it's no longer safe to have the surface ground-down without being retreated.

 

When it comes to irons, if they are in spec for step wear and surface flatness, have no cracks in the sealing groove area and no heat discoloration or "hot spots", I re-use them without lapping. I use a medium-grit ScotchLok pad on a high-speed rotary tool to prep the surface. It de-glazes somewhat without removing much material. I've had very good success with no oil control issues.

 

ooh, an original 2nd gen owner... never met one of those before. Congrats

 

Don't know too many 'old' people do you?

My vert is the second RX I owned.

 

Its not that i dont know older people, none of them happens to be into 7's. Its just all the 2nd gen 7 owners i've met (or *know* thru forums) seem to have bought theirs second or third-hand.