Tales from the Batcave (RX-7, rallycross, misc. stuff content)

On the way to the Batcave, my laptop strap broke.  Between that and wanting a new pair of headphones, I went to Micro Center a half hour on the other side of town.  When I got out, I saw that my car had a twin.

That was neat (and talking to the other R's owner was fun) but we have work to do in the Batcave.

Before the engine goes in, I'd really like to figure out what the hell was up with the clutch not disengaging fully.  There were marks inside the back of the eccentric shaft like the transmission input shaft was hitting it.  At one point the driveshaft had been bottoming out, maybe things got borked?  I measured the transmission's input shaft protrusion from the bellhousing face relative to the most accessible trans on the Rack of Spares and found no appreciable difference.  Hm.  Okay, let's go through the linkage.

Clutch fork pivot ball had some wear and a big lip around the outside.  I filed the lip off and stuck it back on after a thorough inspection for cracks.

Ever since I started using ACT pressure plates (got one free with the car, got another free with a core engine) I had problems with the linkage, starting with breaking the heads off of the pivot ball, so I weld up the pivot ball in-line with the clutch fork.  Needs to be only in-line so the fork retention spring has somewhere to grab.

Next, I thoroughly inspected the clutch fork for cracks.  It seemed okay.  This is one of the ones that I had previously cracked and reinforced after.  Most transmissions don't come with clutch forks for some reason so I use whatever I get my hands on.  I applied a bunch of brake grease to all the pivots and put it back together, with a shrug.

This is totally safe.

Don't try this at home.  Go to a friend's house, or rent a garage almost a half an hour away from your home instead.  (Vise-Grips keep the strap where you want it to be)

For posterity's sake, this is the morphidition of what it takes to use an FC driver's side engine mount on the right side of a GSL-SE intermediate housing in order to put a GSL-SE type engine on an FC subframe.  It broke repeatedly, followed by the adding of more metal, followed by breaking in a different place, followed by adding of more metal...

Okay.  Here we go into overthinking things again.  I have been having a lot of drivetrain vibration issues ever since installing the 9".  Well, not ever since, but they got a lot worse.  So, I am thinking, since the next time I can reasonably drive this car is probably six months from now, that it is a good time to correct one of the glaring flaws/compromises that Mazda made when designing this car.

The design of the car is... confused.  If you look at the tub, it was clearly designed to be left-hand drive because the left footwell is enormous compared to the coffinbox on the right side.  But they massively cockeyed the drivetrain so that the exhaust would have clearance to a RHD steering box or steering shaft.  This is part of why LHD SA/FB have so much left front weight.

This also puts an angle in the front U-joint that cannot ever be reconciled no matter how much one plays with pinion angle.  Given that engine mounting has been an issue ever since I did the FC crossmember swap in, uh, 2010 or so, and I gave up on having an unbroken driver's side mount for so long that I just chain the engine down on that side....  maybe this is a good time to do Better.

Many years ago, i bought a poly engine mount kit from Summit for $cheap.  I think it's for some generation of Wrangler.  Whatever, it looks pretty adaptable, and it was cheap back then and is essentially free now since all it does it take up space on a shelf, so let's finally use it.  Driver's side will go roughly here-ish:

I couldn't easily stick the passenger side there-ish with the header still in the way, but the passenger side will be a bit tricker with the reduced room thanks to my moving the engine about 2 inches to the right:

Text to be added later, food must happen.  Noodles and turkey and A1 sauce, in mass quantity.

(Text added.  Food happened with fried diced potato instead of noodles.  It was glorious)

So now a box end wrench can truly be called a multi tool? I have used mine for leverage on other open end wrenches and as a make shift hand crank among other things but as an attachment point is a new one.

Sometimes it is the only way.

Me at work using a forklift to remove a new centersection from its shipping crate, for installation in a Ford based motorhome.  Cannot remember the designation  but the pumpkin probably weighed close to 300lb, and had four bolts on the drive-side carrier cap.

Had to remove the pinion flange from the old one to swap over the parking brake.  Pinion nut torque is roughly 900ft-lb.  Have fun.

New problem.  I want to remount the engine, which will necessitate hacking and slicing the exhaust, and mucking about with the trans mount to get the drivetrain at the right angle...

...why not use a NA/NB Miata driveshaft and shift the engine and trans back a few inches while I am at it?

The Miata and Series 3 RX-7 pinion flanges share a register.  The Miata has a different bolt circle but here should be enough room for me to redrill.  Racing Beat makes an oil filter pad blockoff for people who want to run an inline oil filter.  The main issues would be neatly relocating the window switches, and if the carburetor would clear the firewall.

But the UPSIDES would be less nose weight, and I could move the rear axle back forward to where it is supposed to be.  Might also be able to fit more radiator in the nose as well.  And, Miata driveshafts are easy to find, while Series 3 driveshafts are not, and you can buy a brand new Dorman driveshaft for a Miata for about what a used RX-7 driveshaft with good U-joints goes for.

There is a NA Miata at the Pick-N-Pull down here. It has an aluminum radiator and aftermarket header that I would have grabbed last time I was there if I had realized it was half-off day before I checked out. 

In reply to EvanB :

Summit had a couple Dorman Miata driveshafts in the clearance aisle a while back.  Bought one on a 25% off day, I think I ended up paying $60 for it. 

Knurled. said:

 

Somewhere, someone is crying.

HA!  Suck it, Vadim!

Much picture dump incoming.

Miata 1.8 driveshaft in background, manual trans Series 3 RX-7 in foreground.  Difference in length from flange tp front U joint is approximately 160mm.

My Holley un-carburetor.  The distance from the bolt pattern to the outside of the linkage mess I have made for myself is about 75mm.  It is about 50mm absolute minimum if I pare everything from the throttle shaft.

160mm of tape is extended.  Oh dear.

This is where things get interesting.  I noted on Randy Stocker's solomiata.com webpage that the 1.6 Miata has a driveshaft that is 48mm longer than the 1.8 and has a bolt pattern 62mm on a side versus 67mm of the 1.8.

48mm less setback than 160mm is about 110mm, which is doable.  As a bonus, the S3 flange appears to be the same as 1.6. Not that it should matter because there is plenty of material on my rearend flange to redrill for the 1.8 pattern, but that's a nice thing.

Another bonus.

It appears that I would be able to relocate the shift tower and the shifter would come up in the same spot.  This is Good because the tunnel narrows significantly behind the shifter hole.

Moving on.

Passenger side as viewed from the fron of the car.   Mount would end up here-ish.  I'd probably attach the bracket to the old idler arm holes in the chassis rather than try to add on to the subframe, as it looks pretty flimsy there.

End of tape measure is where the currently-hanging mount will reside.

The firewall will need some minor clearancing for the clutch fork  but this is nothing not doable with a sledgehammer, no serious fabrication required.

And as I was leaving  I remembered something.

I still have this guy!  And with engine setback, the strut tower would no longer be massively in the way.  Even with moving the engine an inch or two to the left, there would be more clearance.

Head on view.  The engine will be sitting higher so this is great.

On to the other thing I did.  Car has 250k miles, about, maybe more.  I did the subframe swap about 80k ago, give or take, and just slapped the donor car's brakes on it.  The donor car had about 160 or 180k on it, give or take.

Not sure if it is visible  but these have the Mitsubishi logo on them.  These are OE pads.

Not quite going to bolt in.  The bolt pattern is just annoyingly different enough that there isn't room to oval holes OR make an adaptor.

I gave a 1.6 driveshaft to JohnRW a long time ago, he may still have it laying around.

Solomiata sez 1.6 is 864mm center to center, 1.8 is 816mm.

Wish I knew where this info is available from as I am curious now what lengths the S3 automatic are (4sp autos are longer than 3sp so the S3 auto has a short shaft) as well as the FC driveshaft lengths.

S3 manual driveshaft is 967.5mm.  I couldn't tell if it was -67 or -68mm so clearly it's in the middle.

And so, thus, and therefore, combining undoing how I shifted the rearend back 3/8"ish to keep the driveshaft from bottoming out under certain conditions, we're looking at about 90mm of setback with the 1.6 driveshaft, or about 140mm with the driveshaft that I already own and not a $200 unit that I don't have yet.

Or, I could, you know, shift the rear axle more forward than stock too.  That would actually make the springs line up better anyway, since the upper spring seat is actually forward of the axle.  And it WOULD mean using parts I have already on hand instead of buying more.

Front axle is already an inch forward of stock, and I'm moving the rear forward as well, AND getting a bunch of engine setback.  Where have I seen this movie before?

Stacks!  We need STACKS! 

I approve of this random, though appropriate, afx dodge.

Please do so to a mazda.

With a hemi.

EvanB said:

I gave a 1.6 driveshaft to JohnRW a long time ago, he may still have it laying around.

I'm pretty sure he doesn't, and he doesn't have a 1.6 rearend and axles either.

The Miata 1.6 driveshaft does indeed have the same flange as '83-85 RX-7.  Quick measurement suggests that the actual length difference is around 84-85mm.

I have been VERY sick this week (but I'm feeling much better now) so I have done nothing but cough, hack, wheeze, snork, and generally suffer all manner of disgusting-fluid based issues.  I also did some thinking and planning.

And then, this morning, I ground to an abrupt halt, for one very important reason:  I do NOT want to set the engine back, because then the flywheel and clutch will no longer be forward of where I keep my feet.  This is a critical spatial feature should the flywheel or pressure plate decide to fail.  Clutch explosions are no joke.

Interesting that the NHRA requires an SFI scattershield on all rotary powered cars quicker than 13.49.  Which is not very fast at all.

Grumbling, I did the math on how much moving the drivetrain back three inches in-chassis would affect weights, and the difference is about 10-12 pounds per axle.  That's startlingly insignificant.  I'd be much better off doing.... well, there's stuff I'm going to be doing, that will definitely have more effect.

But now I am wondering what it would take to shift the rear axle forward three inches.  Cut the wheelbase from 97 inches (95.5 stock, front axle is 1" forward, rear is about 3/8" rearward) down to about 94.  And shifting axle centerlines does a lot more for weight ratio than moving individual parts because it's shifting the whole car.

if your thinking and planning involved cold meds you may want to review those delusions of grandeur.....

I hesitate to offer this idea, mostly because its really bad, but could you turn the outside of the hub enough to bolt the caliper in? I cant see in the photos how far you have to go and like when the brake disk falls off the hub just remember I told you this was a bad idea....

In reply to Knurled. :

I saw a youtube video of an R100 blow a clutch/flywheel on a dyno run. It about cut the car in half.....

I know you mentioned automatic driveshaft earlier....  if they are anything like the fc driveshaft, the trans side is different and fits the turbo type trans, not the na trans.

In reply to wvumtnbkr :

The SA/FB had two different automatics.  The 3N71 was the three speed, and was the same length and output as the 74-92 manual transmissions (except TII of course).  Driveshafts were the same automatic and manual.

'84-85 got the 4N71, which was the 3N71 with an overdrive stuck between the bellhousing and transmission case, so it was longer, but it still had the N/A sized output.  Driveshaft for auto was shorter. 

TheFC had a 4N71 (and later the electronic controlled version, which was a completely different alphabet soup) with the larger output.

In reply to Bent-Valve :

The rotor height is not why it won't bolt in, the difference in bolt pattern is.  Wilwood is a standard 5.25" pattern, Mazda is something around 20mm further apart.  Too far to oval the holes in the caliper, not far enough to make an adaptor bracket.

I'll see how they work over MkIII Escort front rotors on Ford Contour rear hubs and Volvo 740 uprights.

(er, did I say that out loud?)

Real numbers - Mazda bolt pattern is about 6 3/16", or maybe a tiny bit less.  It didn't add up to a metric number, so this may be one of those things where they hammered an English standard into metric.  This happens a lot with brakes given that most brake hydraulics originated in the UK before they went metric.  (What, you think that brake master cylinder is 22.22mm on purpose?  Of course not, it's 7/8")  Call it 26mm because why the heck not?  26mm is 13mm of offset per bolt, which is a tad more than a bolt diameter, so merely ovalling the holes would probably turn the holes into slots.   If I were to slot, I'd have more luck buying a set of FC or FD calipers and slotting the bolt holes inward so that they would fit properly on my 10" rotors.  (FD and FC front 4-piston interchange, FC 4-piston had 11" rotors, but same uprights as the 10" rotor/sliding caliper cars)

But the FC calipers, despite being aluminum, weigh more than the WIlwoods.  And they are somewhat problematic, with seized pistons common.  And they are more expensive than Wilwoods.  And I already own Wilwoods.

Also, a Miata rack is approximately 26" inner to inner, while an FC rack is approximately 28".  An FB suspension is approximately 24" control arm pivot to pivot.  A lot of hmm.

Retroaddendum:  This car annoys me.

I spent an hour in teh Batcave tonight with a tape measure and increasingly numb fingers in my left hand.  (Damned Reynaud's.  And they lie, merely knowing the demon's name doesn't give you control over it)

Measured from the pinch welds to the trans crossmember/bracket (too small to justify the term crossmember).  Found that the centerline of the trans is actually 10mm left of center.

Measured from strut tower to strut tower.  Used a prybar thisway and thatway.  Even with the front of the engine "centered", not even 10mm to the left, it looks massively cockeyed.

Not trusting the pinch welds, I found the chassis specs in my Haynes book.  It's annoyingly vague, but appears to imply that the chassis rails are symmetrical.  Measured the trans position off of THOSE.  Trans is about 13mm off.  To the left.

With the eccentric bolt centered (not 10 or 13 mm to the left), and a string from the center of the cowl to the center of the front panel, it looks obviously like the drivetrain is kinked with the trans to the right.

Much frustration.  Fingers going numb.  Went to BP to acquire warmables and some fuel because teh S60R was low due to last night's parts delivery/Cheburek acquisition.  Mulled it over while dumping another 15 gallons of yummy 93 octane into teh m00se. 

Halfway home, epiphany.  Duh.  The RX-7 was wrecked when bought.  The front end was visibly shoved over to one side.  NONE of the front body panels lined up.  Of course it doesn't make sense, the front of the car is more crooked than [PATIO]

"What is a Cheburek?"

Let me tell you.  It is a taste experience like nothing else.

Video for how to make a proper cheburek

Advanced edition

As long as the engine and diff are parallel, does the offset matter?  Your u joints should deal with it if the flanges are parallel, right?