New Girling Slave Cylinder
Drivetrain Intro Street Twin page 1 T56 rebuild T56 to TH400 conversion
The 3/4" bore sleeve, piston and seal that George installed in my stock slave cylinder housing the day I visited McLeod World Headquarters was one of only a couple of prototypes. McLeod decided to ship a 7/8" bore sleeve kit with production Street Twins, and offered to send me one. But despite the increased pedal pressure, I liked the shorter pedal travel of the 3/4" bore over the 7/8". If my math is right, pedal effort (how hard you have to push) varies as the inverse of the square of the ratio of the slave piston diameters. Filling in the numbers for the stock 1" slave and my 3/4" slave gives 1*1 / 0.75*0.75 = 1.78, so my pedal is almost twice as stiff as stock. But I don't have to push it very far, which makes for a quicker shift.
The problem with having a prototype, one of them, anyway, is what to do when it breaks. The Hooker long tube collector sits right next to the plastic slave cylinder housing and basically bakes the steel sleeve inside. Since the sleeve is encased in plastic, there is no heat sink available. My piston seal gave up midway through the third 20-minute Street School session at the Thunderhill road race track. We pulled the slave apart at the track and found the seal to be hard and crumbly. So I got to drive 150 miles back home, on Sunday afternoon of the Memorial Day weekend (can you say, heavy traffic?), with zero clutch. No fun.
The following Monday, McLeod told me they had two more seals, which were special ordered for the prototype piston they machined on their in-house lathe, and that I could have one. After receiving it, I got a quote from the local seal store on more. $16 each, minimum quantity of 5, or I could get 10 for $100. For seals! It was then that the resolve to trash the stock slave altogether reached critical mass.
I ordered a 3/4" bore Girling slave cylinder (part number 3520-.75RH) from Pegasus Auto Racing Supplies, and a rebuild kit, for about $60. Hurdle #1 was the stock braided hose, which has crimp fittings at both ends. As shown in the pic below left, the master cylinder has been modified (by my favorite fabricator and ace TIG-man Craig Hill) with a -4 AN fitting in place of the stock crimped hose. He retained the stocker's swivel feature and roll pin retention. If you're having trouble visualizing where this is, the fuzzy shaft near the top is the steering column, and I'm sitting where the engine normally does. The right hand pic compares the new cylinder with the stocker. As you might guess, I've had to fabricate a new, much shorter pushrod.
The four pix below show the new slave and the bracket custom made by Alan "180mph" Blaine. The new setup is all metal, so can use the bellhousing as a heat sink to disperse heat absorbed from the header collector. I've added a small heat shield between the collector and the slave to minimize that radiation. Also visible in the bottom pic is the DEI heat shield tubing I've put over the fuel lines to minimize heat transfer from the headers. Also also visible near the right edge (about halfway down) is the oil pressure sensor which I moved from the factory location behind the intake manifold. The other leg of the tee its attached to supplies fresh oil to the Vortech.
