HELP ! Stuck Clutch Disc or HTOB Air Trapped??

[kitcarbp]

Ok ,since my last post on this topic I havent spent time at all on the car since last November. I'm back at it now and determined I was only getting partial clutch disc release with 0.480-.490" (crude measurement) of movement from my McLeod HTOB. This is with the 3/4" Master and 1.1" of stroke. I think I need no more than 0.100" of ADDITIONAL pressure plate movement to get full release of the disc (I can shift ok now but rear wheels still turn with clutch pedal all the way in, indicating disc is still dragging. The Mcleod states total HTOB movement from full compressed to full extention is 0.890". So with my 0.160" initial gap to PP fingers with piston fully compressed + the 0.480" of current piston movement, I have (0.160+0.480)- 0.890 or 0.250" left until I'm at the end of HTOB piston travel.

ANSWER: I confirmed today it takes 0.575" pressure plate finger compression to COMPLETELY disengage my clutch disc. Clutch pedal to the firewall (full travel) and input shaft fianally stops turning @ 0.575" of HTOB movement !!!!!. But this comes with a too large of a pedal tavel so the 13/16" bore M/C will remedy that situation.

So yesterday I ordered the next size up Master Cyl which is the 13/16" bore which I hope, with the little extra fluid volume will find the "sweet spot" for clutch pedal stoke, and of course, the complete release of the clutch disc. I'll report back after its installed. Pedal force should remain resonable as well.

I have a stupid question for those with these concentric HTOB's. Where do I find the published piston area for the McLeod's HTOB? Do i have to measure it myself ? I have a few extra's left from my intial set-up I can measure.
UPDATE: I could not find any published piston area sizes, So I measured a spare concentric piston for the bolt-on style Mcleod HTOB bearing used on the Tremec TKO. Its a donut shape and I came up with a slave piston surface area of exactly 2.0 square inches.


I also found this article that helps explain how to calculate your clutch set up requirements. Happy reading.
Clutch Calculations

[kitcarbp]

OK, After installing the 13/16" master cylinder for the HTOB I found the sweet spot as far as adjustability for my set-up. While the pedal pressure has increased a bit from the 3/4" MC, its not too much for my young left leg. I may have a different view 10 years from now
I am able to have the clutch disc begin to engage with my pedal about 1 inch off of the pedal stop as its rising up from the floor board. The total HTOB travel I have is about 0.600 inches with the pedal fully depressed to the pedal stop. Shifting is smooth into all gears.
So the root cause here was not a stuck disc NOR air in the system (Im an expert in that task and can fill a new system and have it bled in about 10 minutes tops.) It was simply not enough HTOB travel using the 3/4" MC and my clutch pedal geometry as designed.
I also installed an aluminum coated heat protective sleeve (from DEI) along the complete length of the clutch fluid feed steel line to keep the heat from the headers from boiling the fluid in the clutch line. The next mod I'm doing is to form a basic heat shield that mounts to my master cylinder to keep the header heat from heating up the fluid in the MC. Well...... that sure was an education in custom hydraulic clutch set-ups, if I did this for a livin Id starve.. !!. but its set up right.