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EvanB (Forum Supporter)
EvanB (Forum Supporter) GRM+ Memberand MegaDork
1/22/21 5:19 p.m.

I went downstairs and found this. Which is a bonus because it has the engine mount I was looking for on it. 

I could probably be convinced to pack it up and ship it since being used on a car is better than sitting in my basement for years and then being scrapped when I get sick of it. 

 

1988RedT2
1988RedT2 MegaDork
3/6/21 12:28 p.m.

Well, I decided I'd keep the one I had, since it really didn't look too bad.  Here it is substantially cleaned, substantially straightened, and wearing two coats of POR-15.  It was 21 degrees here this morning.  It will be interesting to see how long it takes to dry.

subframe

1988RedT2
1988RedT2 MegaDork
3/15/21 1:37 p.m.

Well, suspension is finally back together.  New struts, new upper mounts, all new front bushings.

On to the original problem--rebuilding the engine.

Soaked the front iron overnight.  Cleaned up okay.  Except for these pesky gaskets.  They are hard, fibrous and inclined to be one with the machined iron surface.  Razor blade is getting the job done, but it's slow going.

1988RedT2
1988RedT2 MegaDork
3/23/21 10:09 a.m.

Pushing on with cleaning and inspecting engine parts. 

I didn't really notice this on disassembly, but the apex seal slots are definitely wallowed out a bit, and there is a bright lip of metal on one edge.  I'm guessing this is a consequence of running north of 20 psi boost.

How borked is this? With the old apex seal in the slot, I can slip a .15mm feeler gauge in about 2mm deep, so it's definitely Vee'd out a bit.  Thinking I'll just press forward at this point.  

 

 

 

 

1988RedT2
1988RedT2 MegaDork
3/23/21 5:59 p.m.

And just out of curiosity, how aggressive can I get with the rotor?  Is Scotch-Brite too agressive?

Also, if I was re-ringing a boinger engine, I would use a hone to "break the glaze".  Do I want to run an abrasive over the flat surfaces of the irons?  I think the Atkins video makes a reference to a 200-grit flat stone, but they don't go into detail.

Anybody that has done this before got any helpful suggestions?

EvanB (Forum Supporter)
EvanB (Forum Supporter) GRM+ Memberand MegaDork
3/23/21 6:08 p.m.

I have done it before but I was under the supervision of someone who knew what they were doing so I don't have any really helpful suggestions. 

For the rotors I just used solvent and a nylon bristle brush and plastic scraper for the tough stuff. 

Brett_Murphy (Ex-Patrón)
Brett_Murphy (Ex-Patrón) GRM+ Memberand MegaDork
3/23/21 8:11 p.m.

I forget what the exact spec is on a rotor housing/apex seal, but that seems like a lot. You're supposed to measure it with new seals, and was thinking .003 inches about where you want that gap to be.

Racing Beat seems to agree that I was close.

Brett_Murphy (Ex-Patrón)
Brett_Murphy (Ex-Patrón) GRM+ Memberand MegaDork
3/23/21 8:15 p.m.
1988RedT2 said:

And just out of curiosity, how aggressive can I get with the rotor?  Is Scotch-Brite too agressive?

Also, if I was re-ringing a boinger engine, I would use a hone to "break the glaze".  Do I want to run an abrasive over the flat surfaces of the irons?  I think the Atkins video makes a reference to a 200-grit flat stone, but they don't go into detail.

Anybody that has done this before got any helpful suggestions?

I used broken pieces of seal to clean the worst of the carbon buildup in the appropriate groove (apex in apex, side in side, etc) with liberal application of WD-40 and mineral spirit cleaners. A Scotch Brite pad is fine. Remember, all of those seals are sealing outward towards the face of the housing, so getting micro-scratches on the mating surfaces inside the rotor where the springs go won't hurt much.

j_tso
j_tso GRM+ Memberand Reader
3/23/21 10:36 p.m.

You can get aggressive with the combustion faces of the rotor, away from the apex seal groove. The side of the rotor in the photo doesn't look like it needs more than a wipe down with parts cleaner. Like Brett_Murphy said use an old side seal to clean its groove, be careful not to cut yourself.

For the iron faces a scotch-brite pad lubed with parts cleaner should take care of the coolant passage side. I don't think it's recommended to use anything abrasive on the combustion area. Be sure to scrape out any remaining bits of the coolant seal in the grooves, I sacrificed a small flathead screwdriver to do that.

1988RedT2
1988RedT2 MegaDork
3/28/21 5:48 p.m.

I've got the rotors pretty darn clean.  Cleaned up the tension bolts today.    Getting pretty close to starting assembly.

Question on the rotors:  The manual makes reference to a "soft material coating" on the side surfaces, between the side seals and the rotor edge.  If such a coating exists on my rotors, it is well worn, and discontinuous.  Should I be concerned?

doritos

sevenracer
sevenracer Reader
3/30/21 7:44 p.m.

I don't think you need to worry about that at all -  I think any used rotor will look similar, and lots and lots of motors have been built with used rotors.

 

1988RedT2
1988RedT2 MegaDork
4/16/21 10:08 p.m.

Big day today!  My son and I just got finished torquing the tension bolts.  The keg is assembled.  Plenty more to do, but this was a big step.  No left over pieces, and I can turn the e-shaft by hand. 

1988RedT2
1988RedT2 MegaDork
4/19/21 8:55 a.m.

Pics or it didn't happen, you say?

Here's one of the engine, and my impeccably organized work area in the foreground:

keg

1988RedT2
1988RedT2 MegaDork
4/19/21 11:00 a.m.

Ah, shoot!

We interrupt this rebuild to order a new bearing plate for the thrust bearings.  Both of the ones I have show irregular wear on one side.  One has an arc of a "groove" the width of the bearing around about 290 degrees of its circular path.  The other one has two small areas of jagged wear at the outside portion of that path. 

Not going to jeopardize the rebuild for a 30 dollar part.

Should I just go ahead and get new bearings also?

1988RedT2
1988RedT2 MegaDork
4/19/21 11:23 a.m.

I guess I answered my own question.  New thrust bearing set is $37.  Not going to jeopardize the rebuild for a 37 dollar part.  It's on the way.

1988RedT2
1988RedT2 MegaDork
4/19/21 12:09 p.m.

And because the going exchange rate is one thousand words for a single picture, I offer the following:

Plate with two small jagged areas of abnormal wear:

plate1

 

Plate with shallow circular trough from the 11:30 position to the 2:30 position:

 

plate

1988RedT2
1988RedT2 MegaDork
4/22/21 2:46 p.m.

So, one more concern as I'm awaiting the arrival of thrust bearings:  How much scoring is okay on these oil pump parts?  I don't see anything that would seriously compromise the function, but I wasn't expecting quite that level of scoring.  Normal?  Okay?

 

1988RedT2
1988RedT2 MegaDork
4/30/21 10:51 a.m.

Well, dangitall, I'm kind of stuck and getting frustrated.  After receiving and installing the new bearings and bearing plate, I find that neither of the two end play spacers I have gets me sufficient end play.  I've literally got like half of a thousandth with the thicker of the two spacers.  I guess that's to be expected when you put new parts in an old engine.  The spacers I have are apparently worn down some, as both are a bit smaller than they are supposed to be.  I have two different sizes on order at my local Mazda dealer, who said he could get them in by Monday.  Hopefully, one of those will get me in the acceptable range.  Additionally, I bounced the dial indicator that I borrowed from my neighbor on the floor, so I'm buying two of those.

So if you'll excuse me.... 

 

GAAAAAARRRRRRRRRRRGGGGGGGGGHHHHHHHHHH!!!!@XX&&*!!

 

Whew.  Thanks.  I feel better.

infernosg
infernosg Reader
4/30/21 11:18 a.m.

Yeah the spacer game sucks. At this point, I've just started buying one of every size whenever I encounter the situation. I have like a dozen differently sized spacers and shims for when I rebuilt my transmission and a couple different ones from rebuilding my engine. Don't know if you're aware of this or not but the large copper crush washer will affect end play. I was told to reuse the old one when checking end play to select the correct spacer and then use the new one for final assembly.

1988RedT2
1988RedT2 MegaDork
4/30/21 1:01 p.m.
infernosg said:

Yeah the spacer game sucks. At this point, I've just started buying one of every size whenever I encounter the situation. I have like a dozen differently sized spacers and shims for when I rebuilt my transmission and a couple different ones from rebuilding my engine. Don't know if you're aware of this or not but the large copper crush washer will affect end play. I was told to reuse the old one when checking end play to select the correct spacer and then use the new one for final assembly.

Wow.  I'm not sure how I feel about that.  Seems a little iffy, but what do I know?  This is my first rotary rebuild.  I guess I'll go out there and check it with the old washer.

What's your track record on rebuilds?  Sounds like you've done a few.

Edit:  Whoa!  I just checked your profile.  We're practically neighbors!

1988RedT2
1988RedT2 MegaDork
4/30/21 1:20 p.m.

So, I checked the thickness of the two copper washers.  The new one is almost exactly .004 thinner than the old one.  Interesting.

Edit:  After torquing down the front bolt with the old washer, I get the same end play, which kinda makes sense.  I'm pretty sure the only things relevant to end play are going to be both thrust bearings, the spacer, and the plate.  Everything else is just part of the stack.  Torquing the bolt will snug it all up regardless of thickness. 

I think.

 

infernosg
infernosg Reader
5/3/21 8:18 a.m.

In reply to 1988RedT2 :

Cool. There's a few rotary guys in central VA. There were actually 3 RX7s at the Richmond Cars & Coffee this past Saturday though I was the only FC. All still had their 13Bs, too! If you're not too far away I'm always willing to lend a helping hand.

Regarding the washer. Like you, I haven't really noticed a difference in end play between a used and newer washer. Maybe 0.001" max and now I can't remember which way it went. I tend to shoot for the middle of the specified tolerance for this reason. I guess it just goes back to the rule of never reusing crush washers. I'm definitely guilty of reusing them. Usually on oil pan drains plugs and it does seem like they will start to leak after enough reuses. Technically, you can heat up the washers to reduce the effect of any annealing that might have occurred. Just isn't something I want to risk on the engine.

1988RedT2
1988RedT2 MegaDork
5/3/21 1:07 p.m.

In reply to infernosg :

Hey, my son was at the Regency cars and coffee Saturday.  He's got a BMW and hangs with a Porsche guy.  I guess he forgot to take any pics of RX7's.  I'll have to have a talk with him.. wink

Yah, I've basically been sparing no expense on this thing, because I don't want to Berkeley it up.  Of course, there are no guarantees.  laugh

Hopefully, I'll have the new spacers by this evening and I can get this thing moving again.

1988RedT2
1988RedT2 MegaDork
5/3/21 7:38 p.m.

Hallelujah!

The T spacer (the largest one I purchased) puts me at the low end of the recommended range.  I'm done.  Putting the front cover on tomorrow.

infernosg
infernosg Reader
5/4/21 9:02 a.m.

In reply to 1988RedT2 :

Heh, small world. I'm not out there every other weekend but I try to make it when I can. My kids are still pretty young so Saturday mornings are usually reserved for their various activities. I try to alternate bringing the FC and SA. It's funny how they attract completely different crowds...

Glad you got the end play sorted. Are you planning on using the gasket with the front cover? I've started to leave it out and just use RTV. Of course keep the oil feed o-ring (and spacer, if needed). I've found leaving the gasket out and using RTV results in a small bump in oil pressure. I've also started to explore methods of better sealing the oil pump. For my last engine I smeared Hylomar (the real stuff) on the contact surfaces of the oil pump and front iron. It's supposed to be able to seal small gaps and never really dries. I've also seen some guys machine a groove to accept an o-ring on the backside of the oil pump. I may try that with the next build.

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