The Bean

Well, the next priority skipped the line. The clutch pedal has gotten very inconsistent, sometimes not returning all the way, sometimes needing excessive pressure to depress. Assuming that my issue lies in the clutch cable, it is time to convert to hydraulic. First lets get the pedal support out:

While taking the pedal support out, I found the source of the slop feeling that is present when both the clutch and brake pedals are pushed simultaneously. The shaft runs through the inserts you see above, with plastic bearings in the inserts. These pressed inserts have vibrated loose, and have added some slop. So... lets fix that first. Unfortunately they are made of mystery metal, and I don't want to mess with an adhesive here. So... lets remake them:

After welding we need to get them straight again:

Then of course order new plastic bearings. Every project must start with a warm up project.

Although I was planning to use miata master and slave cylinders, the math shows that the 5/8" master would have to travel full stroke to provide enough volume. Instead I'll try out this 11/16" 1994 Corvette master cylinder. Now to decide on a pedal ratio.

^ I beg to differ

 

^ I beg to differ

Just as you should :D

So a bit of ratio calculation:

Current ratio:

3.44 Clutch Fork x 4.1 Pedal = 14.1:1 pedal ratio

Future ratio:

I want to shorten the pedal throw a bit, without making the pedal too stiff. The internet seems to think a 12:1 ratio is ideal, so lets aim for that.

2.92 Clutch Fork x ?Pedal x 1.19 Hydraulic = 12:1

Solve for pedal ratio = 3.46:1

So to place our pushrod point:

10.75" (pedal pad to pivot) / 3.46 (ratio) = 3.11" 

So, weld a nub onto the top of the pedal, and drill a hole.

Next, lets place the master cylinder. But to do that we need a pushrod. Of course we need adjustment, and the proper end for the corvette master. So lets blend the NA miata pushrod with the corvette:

Finally, the first mockup. The angles aren't quite right, but the concept will work.

Skipping over to the transmission side. Nukem was kind enough to send me a slave cylinder bracket to use on my T5 in exchange for some machine work. To accommodate the slave cylinder location the bellhousing needs to be trimmed. So out came the transmission.

While the transmission is out lets pop on the 8 tooth speedo gear to get closer to the right speedometer output.

Also, lets replace the leaking rear main seal. Unfortunately, it looks like the oil pan gasket is leaking in this area as well. That will be a problem for another day.

While we have the transmission out lets splash some paint on the shifter cover flange:

After installing the transmission, it was clear that the miata slave cylinder was interfering with the tunnel. The inlet port was the main offender. This is in the area where your right foot rests while driving, and I'd rather not punch new dents into the tunnel. To try to work around this, I turned a couple threaded standoffs to mount the cylinder upside down:

Unfortunately, there are some tight clearances with this setup as well. It will work if it needs to, but I have some other slave cylinders on the way to try to create a better solution.

2001 Mazda Protege 1.6L slave cylinder is the ticket... (until testing anyway) Duralast part number 10404. I whipped up a new bracket because the mounting pad has a considerable angle cast in.

You can see the valve spring retainer welded to the clutch fork. This was a good idea from my brother, it has a chamfered edge that should be a good bearing surface for the pushrod. Hopefully I didn't anneal the whole thing while welding.

In reply to Shavarsh :

Is that bleeder pointed down?

That will need to be bled with a C clamp around it while it is off the bracket and twisted to bleeder up position. 

What these two distinguished gentlemen have said.  Shudders recalling my slave cylinder bleeding challenges from a few years back.

Not to worry, the plan is to reverse bleed (with the motive bleeder) with the slave flipped over (and clamped). Once bled, it will be bolted back up. I am anticipating needing to level the master during bleeding as well. There isn't enough room above the slave to use the miata unit, which would have the bleed port properly positioned.

Next up, weld out the master mount:

After some paint and assembly, the pedals are ready to return to the car:

Impressive work as always.

That looks like it could be a factory application.

Very nice!

Thanks all, your comments are much appreciated.

Assembled and bled:

There is still some air in the system because the master should be able to overtravel the slave, and the slave isn't overtraveling. It can't be much though, as the clutch is certainly disengaging fully. I'll wait until I finish the pedal stop before bleeding again.

Initial test drive impressions:

The pedal effort is definitely higher than before. Possibly higher than I want to live with. However the travel is now ludicrously short (which I like). I'll drive it for awhile before making any changes.

Well, we are leaking from the thermostat housing again. Let's try again before getting a new water neck.

A bit of luck with the fly cutter gave us a shrink fit. This should make it far easier to install the housing without dropping the thermostat!

Have no fear the thermostat was removed and reinstalled with the bleed hole up. Also, I'm really not sure what metal this is. The chips were not a consistency that I recognize. I'm not surprised that it warped.

Back on the road!

Just read and re read the entire thread over the last several evenings. Grassroots Motorsports gold!

Shavarsh said:

A bit of luck with the fly cutter gave us a shrink fit. This should make it far easier to install the housing without dropping the thermostat!

That's handy. We just did the whole dropped thermostat dance, super annoying.

On the clutch system bleed vs travel, I have never gotten 100% calculated travel from the Miata slave in my conversion, no matter how much bleeding I have done. I chalked it up to tolerance stacked losses and moved on as it is fully functional and has an acceptable feel.

Nukem's slave bracket is a nifty part. If I was using a Fox bellhousing instead of sn95, I would have grabbed one also!

Thanks tripower and gumby! 

The thermostat installed nicely due to the shrink fit. I'm also trying "the right stuff" this time because ultra black let me down last time. The thermostat seems to be opening at 200 instead of 190 now, so it might be a bit pinched, but it could be confirmation bias.

After driving for awhile the clutch effort feels very reasonable. The wife commented that the feedback is improved and it feels more modern. I'm pleased!

Your work continues to impress me. The level of refinement and thought you're putting into this whole car is just amazing

This car would have been so much more fun 30 years ago when everyone still remembered Pintos as common cars. Remember this comment next time it makes you laugh.