hrcslam

I bought a McLeod Street Twin off Craigslist for a steal of a deal, $300. But it didn't come with the Master Cylinder (MC). Trying to save some cash I decided to try a smaller Slave Cylinder (SC) instead of a larger custom master cylinder.

I found that the Fiero SC has a 15/16" bore vs the stock LT1 SC of 1" (there is an option for a 1-1/4" slave cylinder, but that's not factory). This gives an additional .050" of throw at the PP.

The Fiero SC has bleeder on it (yay!) and a similar bolt pattern, but the pattern is smaller than the LT1, so I had to make an adapter plate.

The LT1 bolt pattern is 2.920" hole center to hole center, with 3/8" holes.
The Fiero bolt pattern is 2.165" hole center to hole center, with AN5 tapped holes (5/16-24).
I clocked the two bolt patterns ~90° apart which allowed the Fiero SC to install with the bleeder valve straight up.
The center hole for the SC pushrod and boot is 1.465"
I shaped the adapter (made from 1/4" thick 6061 Aluminum I found laying around my hangar at work) to contour match the LT1 Slave spacer sleeve and the Fiero slave cylinder. Although I could have left it as a parallelogram. But I figured this would look more factory and I had time to kill waiting for parts.




I fabbed up the part using the Fiero SC and T56 LT1 SC Spacer and never took any measurements. Then before I installed it, decided to trace and measure it out on something and my tool box was right there with a permanent marker, LOL. So that's why the drawing is all messy.



Once I installed the plate to the slave cylinder, I shaved the mounting bolts flush with the plate (I installed the mounting bolts with lock washers). It was either shave the bolts or notch out the SC spacer, and the bolts are a lot more common. If they aren't shaved they will hit the SC spacer.






Now it bolts right on to the T56, with the stock slave spacer and hardware. The pushrod just pulls out of the boot (most slaves are like this), so I pulled the Fiero pushrod out and took the LT1 SC pushrod and installed it into the Fiero slave (without the boot) to see how it fit on the plunger. Looked good to me. So the boot when back on with the LT1 SC pushrod (for the plastic ball end to sit in the Fork).

Next I had to figure out how to plumb it up. This took some trial and error, but I got it figured out. The Fiero slave has 12x1.0 female fittings and the stock LT1 has the quick disconnect fittings. No Beuno, and don't bother trying to convert the QD to AN anything by cutting the hose and installing -AN hose end fittings; the freaking stock line is metric or some ****. It's between a -3AN and -4AN hose size.

So what I ended up doing was replacing the hose from the MC to the SC with a 24" -3AN hose and the T56 AN3 to QD fitting. Then I put a AN3 to 12mm Banjo hose end fitting on the slave with a M12x1.0 Banjo bolt that I had to shorten to not shank out in the SC. I then polished the Fiero SC (with a high speed and a red scotchbrite pad) surface where the Banjo bolt/fitting would sit against, by hand until it was flat. I'm sure a machine shop could do this more accurately, but this worked just fine (no leaks). I sealed up both sides of the Banjo bolt/fitting with 7/16" o-ringed washers (like the ones used for A/C systems).





With everything installed, I gave it a test run and all is good so far. No leaks and it fully disengages my McLeod Street twin.

So here's what it costs (minus labor).
6"x6" 1/4" 6061-T6: $16+ shipping (I got mine for free though)
Fiero Slave Cylinder: $14.41 + shipping (Rock Auto: Centric 138.62009)
-3AN 24" Steel Braided Hyd. Line: $11.99 + shipping (Speedway Motors: 91031845-3)
AN3 to QD Fitting (T56 LT1&LS1): $13.99 + shipping (Speedway Motors: 5151396) Only 1 needed for the MC.
Stat-O-Seal (o-ringed washers)- 7/16": $7.96(4ea., but only 2 are needed) + shipping (Speedway Motors: 6179061)
Total: $64.35 + shipping.

So it's about twice as much as the cheapest Stock SC to do the swap. But 1/2 the cost afterwards for replacements. And it add a bleeder screw and additional throw to the PP (if it's needed). It's about 5 times less than a 13/16" MC.

Side Note: I also shortened the fork T-Bolt .100" while doing this swap with the McLeod Twin Disc, so I don't know if it will have any Fork to PP clearance issues stock. The Fiero SC adds .085" of throw to the SC Pushrod and .065" of throw to the PP. Comparatively the McLeod 13/16" MC adds .107" to the SC pushrod and it's been reported to contact the Twin Disc PP at full clutch release (the Twin Disc is about .500-.600" thicker than a Single disc set up).

Here it is all installed. If I ever need to go back to stock, all I need to buy is another AN3 to QD adapter and the stock SC. This is a bolt in now.

















UPDATE: Adding the Jeep SC (P/N: CS37793) to this.

Posted below too. The Fiero slave cylinder ended up being not enough disengagement for the McLeod Street Twin I have. So I went with a smaller still SC. This time from a Jeep Cherokee 2.5L (SC P/N: CS37793). This uses the same adapter plate as the Fiero, just remove the Fiero SC and install the Jeep SC on the adapter plate. Everything bolts up the same. The stock LT1 SC pushrod is still used with the Jeep SC too.

The plumbing is different though (easier). The Jeep SC is provisioned for a 7/16-24 hydraulic IMF (inverted male flare) fitting. So I got a 7/16-24 IMF to AN3 adapter and a AN3 90° fitting. With those adapters the plumbing was straight up and easy.

CAUTION!!!! I don't have PP clearance issues (no contact between the clutch fork and the PP), but my T-Bolt is shortened .100". If you do this I definitely recommend you shorten the T-Bolt.




Jeep SC on the Left, Fiero SC on the Right.

stevo9389

How much ground clearance does that leave now that the line is run under the slave? The bottom looks almost even with the header and oil filter but angles could be deceiving.

hrcslam

I didn't see any ground clearance issues. I'll get better pictures later today and post em up. But the lowest part of the SC is still higher than the bottom of the bellhousing, which is higher than the headers. At least it looked that way to me, lol. I'll post pics later today.

hrcslam

Here's those pictures showing the ground clearance.

VoyagerCamaro

Awesome idea, nice fabrication too. It'd be nice if you could sign a deal with a aftermarket company to make this in bulk. I will for sure try this when my slave goes out. It'll probably be a while though, just replaced it.

hrcslam

The Fiero slave cylinder ended up being not enough disengagement for the McLeod Street Twin I have. So I went with a smaller still SC. This time from a Jeep Cherokee 2.5L (SC P/N: CS37793). This uses the same adapter plate as the Fiero, just remove the Fiero SC and install the Jeep SC on the adapter plate. Everything bolts up the same. The stock LT1 SC pushrod is still used with the Jeep SC too.

The plumbing is different though (easier). The Jeep SC is provisioned for a 7/16-24 hydraulic IMF (inverted male flare) fitting. So I got a 7/16-24 IMF to AN3 adapter and a AN3 90° fitting. With those adapters the plumbing was straight up and easy.

I don't have PP clearance issues (no contact between the clutch fork and the PP), but my T-Bolt is shortened .100". If you do this I definitely recommend you shorten the T-Bolt.




Jeep SC on the Left, Fiero SC on the Right.