Big Block Ford Hydraulic Throwout Bearing

Hello Matt,
Havent been to active with the Pantera for a while, I wanted to thank you for posting the drawing of the throw out bearing! Thank you !!!

How's the build going?

Regards Mark

Mark,

Thank you, I hope that you find the layout useful. I haven't bled the clutch yet, so I can't report on how well the new throwout works. I have put a new post to the gallery of my car, with new pictures. I was so close to starting the car before the snow started flying!

Sincerely,

Matt

Matt, FWIW your McLeod throwout mechanism looks very similar to the Tilton assembly I've been using since 1992. Tilton supplied these with threaded aluminum front bearing retainers only for T-10s, Muncies and Jericho trannys for dirt track racing, so I built a billet ZF retainer and got the system to work with a 351-C. My problem was exactly opposite: with a stock clutch, flywheel & bellhousing, I had almost no 'spare' room between the outer end of the Tilton and the ZF bearing retainer, when things were adjusted per specs. Are you running a stock Ford motor-protection plate between the block & ZF? That plate introduces 0.190" more length to the system. If you felt confident the clutch would NEVER blow, you could dispense with the plate & suck the ZF & throwout in that much closer. Or just have someone make you a longer threaded front retainer.

Bosswrench,

Thank you for the advise. I am using the aluminum motor-protection plate that came with the Quicktime bellhousing. This plate is depicted in the layout, but not pointed out. The more I think about it, the more I believe that I will need to pull the transaxle out and have a new throwout bearing spacer made. My fear is, with such little thread engagement between the throwout bearing body and the bearing spacer, the threads will be overloaded when the clutch is released.

Tilton says (and I believe them) that the single most critical dimension in an annular-piston throwout system is the 'free play' between the annular piston being bottomed in its bore. If the piston bottoms, it starts spinning with the clutch and those special seals are not designed for rotation, only straight-line motion. So within 50 miles, the seals wear out and total clutch function is lost. The systems are rebuildable but certain parts aren't easy to install correctly; Tilton will rebuild mine for $125. It also gets a bit tricky to set the clearance because when the engine, bellhousing/clutch and ZF heat up during a nice hard run, all the dimensions change noticably. Tilton recommends no less than 1/8" of free play at 'normal' operating temp, which with your system seems to make things worse. I definitely would check into getting a new nose/seal piece made with more threads! There's a LOT of force pushing on those threads during normal clutch operation.
All the Pantera vendors used to sell much the same system a couple of decades ago, but Pantera owners typically don't set them up properly and warranty returns caused all the vendors to stop selling annular throwout systems. The last one I remember being sold was by D. Quella in CO.

Not to discourage you; I like my system, its 8 lbs lighter than stock and far less mechanically complex, with almost no friction. A stock 11" clutch works very easy with a stock clutch master cylinder size. But it also requires the ZF to come out if anything at all needs attention.