Hmmm. Well here is my take for what it is worth. The environment in the bell housing at 7000 rpm is hectic to say the least. Winds of 240 mph sailing around in a tiny volume housing the friction plate, pressure plate, flywheel and clutch slave cylinder with throw out bearing on top. The pressure plate fingers mlve about 12 to 15 mm when engaved with the clutch pedal on the floor. About 2mm of slack, then contact. This motion gives the friction plate about 1 to 2 mm of freedom so a shift can be made. The leverage of the clutch fingers is about 5 or 7 to 1. So, what in this clutch assembly, that heals within 30 seconds, will let the clutch pedal stay flat on the floor then magically recover? Well, the friction plate could expand 1 to 2 mm and then cool which might allow this. Such behavior would immediately debond the friction material amd destroy the friction plate, so not likely that is happening. Next in line, soft clutch hydraulic line. The story is this gets hot and expands with pressure so during repeated applications of the clutch this line gets larger and larger to the point all the spare fluid in the master cylinder is in this bulging hydraulic line, clutch is on the floor etc. Perhaps but this line is well insulated under the car and has never been reported to fail that I know about, which virtually all bulgimg plastic items do sooner or later. Granny spring has almlst no effect on my clutch feel so took it out. Hard to believe its the issue. Brake fluid. Shelby is marketing a seperate brake fluid reservoir for the clutch for this Mustang. With brembos on this car, a fluid flush is a gallon of fluid more or less. Going to 5.1 at $18 a pint means $150 to assure a less hygroscopic and much higher boiling point fluid. A seperate fluid reservoir from Willwood or equivalent is $25 plus the trouble of making a mount. The rationale is simple, this happens at high rpms with great repeatability. Under these conditions, the small volume of air in this bellhousing is HOT. As are all the interior components - the flywheel, the clutch friction plate, the pressure plate, the throw out bearing and the fluid in the slave cylinder. If that stuff boils, and wet dot 3 certainly is likely to, then your clutch pedal sits on the floor until the system recovers. There is a bleed and fill hole in the clutch master cylinder that will allow this boiling high pressure fluid to escape into the reservoir when the pedal comes up first time after boil ocuurs. This pushes any fluid above the bubbles out into the master cylinder and allows the rest to recondense and keeps the pedal on the floor - I think. Just my take. After many consecutive hard runs, mine is fixed.
