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Pete. (l33t FS)
Pete. (l33t FS) MegaDork
12/14/20 4:51 p.m.

More project backlog clearing.

Enter one (1) Volvo angle drive, for P2R with the TF80SC transaxle.  Unit had very loud pinion bearings, and could be felt as "indexing" when turning pinion flange by hand.

First, we mark the carrier bearing adjuster nut and lock plate with a chisel.

Then remove.   Ooooh, this isn't good.  The race is moisture damaged, and the race spins in the housing.  I would think it should be a press fit.

Zip off a bunch of M7 bolts and pop the small case half off.  Lots of schmutz.

Remove the carrier from the large case half, dumping a half quart of nasty gear oil on the bench.  Other carrier bearing outer is junk.  And look at all the metal in there.  If this was an MP3 it would be power chords and double kick drums.


Splines that mate with the collar are over half worn.


i am thinking that this unit may not be worth the bother of disassembling further, and then trying to source bearings that aren't listed anywhere because it is serviced as an assembly.

TurnerX19 SuperDork
12/14/20 7:26 p.m.

At least try to source the bearings from a domestic bearing supplier. SKF in particular does make some that they will only sell to a specific OEM, but you won't know if you don't try. The splined shaft is another issue that looks expensive to duplicate locally.

Pete. (l33t FS)
Pete. (l33t FS) MegaDork
12/14/20 7:38 p.m.

In reply to TurnerX19 :

The splined shaft is a single unit with the ring gear.  It is available as an angle gear assembly, retail something like $1900.


One of the guys who works at the factory in Norway that makes these for Volvo is/was a member of Swedespeed.

Pete. (l33t FS)
Pete. (l33t FS) MegaDork
12/21/20 6:14 p.m.

Heh.  picture backlog.  Woops.


Big baller here, buying genuine Volvo axle.  Because nobody else offers one.

For some reason the car now squats on the right front? I dunno.

Anyway.  While I wss doing this, I did something else...

Volvo-boxed coils and spark plugs.

Old plugs (8000mi old)

A little salt on them.


The axle bearing was a massively tight fit in the housing, which is probably why the old one failed.  I guess the 6 speed auto had a sliiiightly larger bearing than the 5 speed auto's axle.  So, I went out to Batcave-annex and grabbed the housing from the original engine.

R on left, T5 on right.  Note the difference in lower bolt hole.  For some reason the T5 had three M10 bolts while the R had two M10 and one M8.



Attacked the R housing with my new Matco hyper-step drill bits.

OMG these drill bits are awesome

13/32 bit just WHOOOMPHed through the housing like it was cheese.  Large swarf flying. It was glorious.

And, yes, if you are working on a drive on rack, there is enough room to pop the intermediate out enough to get the housing out.  

And the housing now bolts together tightly without compressing the bearing!


Well, that was a $700 lesson.  New rotor housings for the black RX-7 are thus delayed a bit.

Pete. (l33t FS)
Pete. (l33t FS) MegaDork
12/23/20 7:03 p.m.

Volvo likes the new coils and plugs.  A lot.

Not bad for a hyperboosted 300hp fat-assed all wheel drive car.

Pete. (l33t FS)
Pete. (l33t FS) MegaDork
12/26/20 4:18 p.m.

I want to get started on the Quantum.  I'm really motivated to start back on it.

But I will not do that until the 12A for the '81 is an assembly, and not a parts explosion in the garage.

The next step in the 12A is the part of engine building that I really don't like, because it is tedious and time consuming, and it is easy to avoid that when it is freakin' cold in the garage.

And thus, the stalemate is broken.

LET THERE BE HEAT! (And my tablet is really intolerant of light levels)

It's not super awesome, but a hell of a lot better than radiant heat, oddly enough, when your garage is a place to go to only a couple hours a day at most.  $99 at Home Depot, 30k-60k BTU.

And now, for the fun part.  Side seals.  They are select-fit parts, and while the spec is something hilariously wide like .002-.008" gap, if you want an engine with excellent low range and mid range torque, as well as fuel economy, you need to get the chamber sealing as good as you possibly can, and this means minimizing seal gaps.  The low rotor speed means there is more time for compression to bleed off compared to a piston engine, and sealing a square edged chamber is really hard compared to a cylinder.  Anyway, for best results I like to go as low as .0015".

I measured the arc length of every side seal slot, then starting with the longest one, installed a corner seal spring and corner seal at both ends, a side seal spring, and the goal is this:


I wanted to use the Amazing Pile of Junk's side seals, because believe it or not they were new (.140" height), so I measured its slot lengths (well, arc-lengths) and went on down the list trying to find good fits.


A lot of the APoJ engine's seals were clearanced very sloppily.  I ended up grabbing some seals from the spares pile from the '81s original 12A (which appeared to have been a recent rebuild, judging by the rotor housings).  Annoying was when I'd get a perfect match, then measure the height to find that it had taper wear, from dust ingestion.  (The air pump had been removed and the port in the air cleaner taped off, not plugged, so dust got inside and wrecked everything.)

I ended up grabbing a couple seals from the GSL-SE parts engine I acquired about five or six years ago, but a couple hours later I got to here:

Next up: Digging through the piles to see if I have anything better than the severely notched corner seals in the APoJ engine.  But that is a tale for another post.

wvumtnbkr PowerDork
12/27/20 9:43 a.m.

Wait, I'm not so in tune with SA and FB engines...


You are rebuilding a 12A, but used some seals from the GSL SE?  I know the 5 letter car is a 13B.  Do they share sideseals and stuff?

Pete. (l33t FS)
Pete. (l33t FS) MegaDork
12/27/20 10:50 a.m.

In reply to wvumtnbkr :

'74-85 12A and '74-85 13B are the same engine for everything not related to rotor width.  For a few years in the 70s, they used the same part number for side housings, too, and I am fairly sure that the 12A Turbo used the same intermediate housing as the GSL-SE, and the 12A 6-Port used the same end housings too.  The letter has nothing to do with engine family.  There was a 13A, and it had no relation at all to the 10A and 12A.  The 13B is a longer 12A, but the 13A name was taken, so 13B.


The only gotcha for 13Bs is '85-earlier had 3mm apex seals and 1mm side seals, '86-up had 2mm apex seals and .7mm side seals.   Which is why my bridge ported engine (GSL-SE rotor and intermediate housings, 12A end housings and front cover) uses rotors from an '86-88 engine.

Pete. (l33t FS)
Pete. (l33t FS) MegaDork
12/27/20 6:36 p.m.

I'm leaning more and more toward a pair of 45 DCOE-pattern throttle bodies for the '84 when the bridge port goes in.  There will be two pains in the ass.  One, obtaining an airbox that will both fit the chassis AND be well-sealed for dust intrusion.  Second, I'd probably be forced to run TPS-based fuel injection, and I've never been able to get noise levels properly reduced on Megasquirt.


But... I know there's about 30hp locked away in the Holley/cone filter setup I have right now.



The amusing part is that I want to finish the '81 because I believe I can be just as fast with a stock port 12A in a lighter, nimbler car, than the precision-of-a-sledgehammer car that the '84 has become.

Pete. (l33t FS)
Pete. (l33t FS) MegaDork
12/29/20 7:21 p.m.

Corner seals.  The ones from the APoJ engine are egged out worn out junk.  The ones from the 81's engine were in remarkably good shape.  So, I grabbed the corner seals from the engine's seals bin...  and found seventeen corner seals, some heavily worn.  The wear pattern looks like this:


Combustion pressure gets into the side seal groove and forces it harder against the side housing, just like how piston rings work.  The corner seal holds the side seals in place in the rotor, so all that friction causes a wear mark on the leading side of the corner seal.  The goal is to sort the seals into "left hand" and "right hand" seals.  After removing the obviously badly worn ones like this, magically I had twelve left over, and there were six lefties and six righties.

I oriented them so that the unworn side is pushing on the side seal.  This is because these seals were not from these rotors, and so the wear groove is going to be not exactly in the right spot.


At this point, I am just waiting for the package from Atkins to arrive.  Really hoping to see it tomorrow.

Pete. (l33t FS)
Pete. (l33t FS) MegaDork
12/30/20 6:16 p.m.

Atkins package did not arrive.  Spent a while in the Batcave just looking at the Quantum's front suspension and muttering at chunderheaded German engineers.  The geometry is pro-dive for braking.


But, the uprights are weldments.  I have an Idea.

Pete. (l33t FS)
Pete. (l33t FS) MegaDork
1/4/21 12:54 p.m.

Mail's here.


i decided to go with an entire gasket set for a few reasons.  I already needed to buy several important gaskets and O-rings (intake manifold O-rings are a weird size), and for Not Much More, I could get a whole set with Mazda coolant O-rings, the annoying tension bolt washer/gaskets, and the rear stationary gear O-ring.


Also in the package are Mazda oil control O-rings.  Have had very "good" luck with Atkins O-rings, in that after any run time at all the outers would be broken. 100% rapid failure rate. So, sucked it up and paid $160 for Mazda instead of $40 for Atkins.

Pete. (l33t FS)
Pete. (l33t FS) MegaDork
1/9/21 4:21 p.m.

Moving along, needed to take a glory shot.  This simply does not exist in the wild anymore.


Apex seal slots are usually hammered out junk, waaaay larger than max tolerance.  Usually way larger than can be used with .003" oversize Goopy seals.

These are all .002".  Not .0025", but .002".


Not pictured: all the ultra boring tedious stuff like chasing all the threads and the tension bolt threads, rebuilding the oil metering pump, cleaning and repainting the oil pan, blah blah uninteresting tedium.

So what's your take on the current state of rotaries?  Is it soon going to be impossible to find good parts to keep them running?

Clearly they're not nearly as common as 20 years ago, so the expert rebuilding knowledge like you have is likely going away too.

Will most RX-7s be swaps in the future?

wvumtnbkr PowerDork
1/9/21 7:15 p.m.

I'm not sure, but I believe parts for the 13b and renesis are still available.

Pete is building a 12a, iirc.  

Pete. (l33t FS)
Pete. (l33t FS) MegaDork
1/9/21 8:19 p.m.

12A stuff has been NLA for a long time.  Rotor housings and rotors were the main wear items and they would sometimes lose the chrome on the rotor housings fairly quickly.


13B stuff is surprisingly still available.  Mazda North America still has a decent sized stock of GSL-SE rotor housings and apparently Mazda still makes them, along with complete FD engines.  (New, not remans)

Pete. (l33t FS)
Pete. (l33t FS) MegaDork
1/11/21 9:01 p.m.

Accidentally found a pic of the '81 from close to fifteen years ago.


Pete. (l33t FS)
Pete. (l33t FS) MegaDork
1/16/21 5:50 p.m.

Browsing eBay for Audi stuff, found an MC2 fuel distributor assembly marked down 70% since nobody wants them anymore.



I have a complete MAC-14 wiring harness.  The intake manifold as-supplied is meant to clear a fuel distributor, and mount an MC throttle body.  I also have an ur-q fuel distributor igloo.  I have the injectors and rest of the stuff needed to make it work.


$80 shipped, versus another $2000 in bits and bobs to make it injected as well as making a different intake manifold with a larger plenum.


Buy It Now may as well have been labeled "fark it".

Pete. (l33t FS)
Pete. (l33t FS) MegaDork
1/17/21 5:09 p.m.

This is the last time I use Mazda coolant seals and Hylomar.  What a pain in the ass.



For extra fun, the tension bolts that I chased all the threads on and cleaned up for NEW sealing washers, turned out to be from a 13B, even though they were in a box full of the original 12A's stuff.  So I rapidly cleaned and chased the tension bolts from the Amazing Pile of Junk, because all that sealant was setting.


Assembling an engine is a rather stressful two hours.

Stampie (FS)
Stampie (FS) GRM+ Memberand MegaDork
1/17/21 5:26 p.m.
infernosg Reader
1/18/21 3:48 p.m.

Hylomar is some nasty stuff but my God is it GOOD! I use it on any gasket/seal that might see coolant. Such big time when I have to replace a water pump or something but I've never had a leak using it. I even put it on the contact surfaces of the oil pump and front iron since it supposedly is capable of sealing small gaps. Figured it's about half as good as machining a groove for an o-ring.

Pete. (l33t FS)
Pete. (l33t FS) MegaDork
1/18/21 6:18 p.m.

Truth be told, this is only the second engine I've built with Mazda coolant seals.

The first was the first engine I ever built, a street ported 12A for my '80... in 2001.  After that was my peripheral port engine that I used 18 gauge electrical wire per Lynn Hannover, with Right Stuff as a sealant, along with a few other subsequent engines: a street ported Turbo II that I had apart several times, including to bridge port it, a heavily street ported FC 6-port that suuuuucked and died from dust ingestion in one weekend, a bridge ported GSL-SE engine that I had apart a couple times...

After that, I used the Viton material from McMaster-Carr for the full bridge 4 port 13B that I built in 2012.  That engine lasted a loooong time, because I had learned to be relentless in keeping the air entering the engine surgically clean.  All subsequent engines (one rebuild of the bridge port, the experimental GSL-SE "stock" port in the car now, and Evan's engine) were with this material.


I have a feeling that Hylomar does not work very well when it is 30 freakin' degrees in the garage smiley


I only used the Mazda seals on this engine because I had no excuse not to: The rotor housings were not a corroded mess, and the refinished side housings obviously had no pitting where the coolant seals sit.  All the other engines had corrosion to some degree, so they got Right Stuff.  The bridge ported GSL-SE was an engine I bought in parts for $100 that had been in a car sitting in Texas for 20 years.  The water jackets were full of this nasty crystallized green jelly and some of the seal lands in the water jackets were pitted through to water.


THAT engine is why I am anal about cleaning/chasing the threads in the front end housing and on the tension bolts.  When I torqued it up, some of the bolts were springing back.  I was in a hurry and figured, well, okay.  First time the air temp got below freezing, the engine was "loose" enough that it burned the 18 gauge electrical wire.  Oops.  Funny how there's no time to do it right but plenty of time to do it twice.

Pete. (l33t FS)
Pete. (l33t FS) MegaDork
1/18/21 6:43 p.m.

Next time, at the Batcave:

Rallycross Rules, Prepared class allowances, 3.3.D.14:

Pete. (l33t FS)
Pete. (l33t FS) MegaDork
1/25/21 8:46 a.m.

Okay.  Picture heavy time.


On the right is a '81-85 12A intake manifold.  On the left is a '79-80 intake manifold.

All rotaries stutter under light load.  The more port overlap, the more they stutter.  Bridge and peripheral ports stutter driving down the highway, stock ports stutter when coasting down in gear.  So Mazda took the decent manifold on the left, and blocked off the primary-secondary communication channel for the rear rotor, installed a butterfly under the primary barrel, a large communication passage under the butterfly, and a failure prone valve that simultaneously closes the butterfly and redirects air pump air to the rear rotor. 

This all sucks for flow, so we're going to use the '79-80 manifold.  But there is a catch.

81-85 engines have a passage under the primary intake ports for air injection to the exhaust ports.  '79-80 did not have this because exhaust port air was first pumped through a coaxial heat exchanger to heat it up before it got to the exhaust.  Upshot is, you install an early manifold on a late engine, you get a large exhaust leak.

Pete. (l33t FS)
Pete. (l33t FS) MegaDork
1/25/21 8:57 a.m.

It is not all roses with the early manifold.  There's still all sorts of bumps and occlusions and stuff.


Main thing that annoys me is this big dent in the port for a passage from the rear primary port to the air control valve.

The secondary ports are full of weirdness that needs to go away.


On with the JB Weld!  Intake gets a whole tube in the rear primary, paying special attention to make sure the passage gets filled.

While that sets, porting of the secondaries begins.  It doesn't take long to port down to air, or in this case, epoxy.



Now, on to the exhaust leak.

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