HELP ! Stuck Clutch Disc or HTOB Air Trapped??

[mpanten]

Originally Posted by patrickt

Not really. My Tilton 7/8 really doesn't have any more noticable pedal effort than any other big clutch car I've driven. Pics of it are in this recent thread (where I had to remove it) So, Should I Replace This Part or Not?

Agreed,

I use a 1 inch master and it's not a problem. I would just change the master and be done with it. As far as the bleeding goes have you tries pushing the air up through the master rather than pulling it. All you need is an oil can and some hose. Works fantastic

[mpanten]

Originally Posted by patrickt

Not really. My Tilton 7/8 really doesn't have any more noticable pedal effort than any other big clutch car I've driven. Pics of it are in this recent thread (where I had to remove it) So, Should I Replace This Part or Not?

Agreed,

I use a 1 inch master and it's not a problem. I would just change the master and be done with it. As far as the bleeding goes have you tries pushing the air up through the master rather than pulling it? All you need is an oil can and some hose. Works fantastic.

[kitcarbp]

Guys I discovered another issue that I need to remedy, @ .450" of HTOB travel and 1.1 inch of MC stroke, my clutch pedal is now bottomed out against the firewall. (still need to check if clutch disc completely releases tonight)

The way the builder set up my clutch pedal, at the top of travel the clutch pedal pad sits about 2.25 inches BELOW the height of the BRAKE PEDAL pad. I dont like this. My preference is (when both pedals are released) the clutch pedal pad should be the same height or a little (1/4") above the brake pedal.

I too have looked at the 13/16" Wilwood MC, that would be just enough to get the full 0.500" HTOB travel and a tad more if needed with 1.1" mc stroke. If my math is right the 3/4 MC gives a slug of fluid volume 0.485 cubic inches compared to the 13/16" bore MC that gives me a slug of 0.570 cubic inches. Pedal force will go up if I jump up to a 13/16" mc but not too much. I dont think the 7/8" MC is needed in my application.

Patrickt, Mine is a concentric slave, I have no clutch fork, pedal effort relates to combo of the master/slave cylinder diameters, a 7/8" MC on my MCleod concentric HTOB set-up would increase the pedal effort way higher than I want. The sweet spot for my set-up just may be the 13/16" MC. we'll see
Thanks for the inputs.
More later.

[patrickt]

Originally Posted by kitcarbp

Patrickt, Mine is a concentric slave, I have no clutch fork, pedal effort relates to combo of the master/slave cylinder diameters, a 7/8" MC on my MCleod concentric HTOB set-up would increase the pedal effort way higher than I want. The sweet spot for my set-up just may be the 13/16" MC. .

Sounds good. Keep us posted as it's an interesting thread. Although I would have thought that a 7/8 MC would feel the same on a HTOB as it does on an old fashioned set up.

[kitcarbp]

Ok, After removing the "RETURN" stop on my clutch pedal ( allowing pedal pad to be higher and more even with brake pedal pad when released) I was able now adjust the pedal linkage to get 1.1xx" (give or take) stroke on the 3/4" Master Cylinder, which is the advertised maximum stroke. This now moves the HTOB enough to be able to shift gears, finally ! BUT, the disc still drags with clutch pedal to the floor in gear and I am not yet getting 100% clean disc disengagement, which tells me the air gap between disc and pressure plate is not yet @ 0.050". I need to now measure HTOB travel again. Boy I wish I had a lift ! I am now leaning toward getting a 13/16" master so my clutch pedal travel is not so far.

Patrickt- Found the rubber grease you mentioned. Its assembly lube used when rebuilding hydraulic cylinders so you dont scuff the rubber piston seals etc during assembly. Pegasus Racing sells i for $9 /tube. WIll add this to the tool box wiht my next order !

[patrickt]

Originally Posted by kitcarbp

Patrickt- Found the rubber grease you mentioned. Its assembly lube used when rebuilding hydraulic cylinders so you dont scuff the rubber piston seals etc during assembly. Pegasus Racing sells i for $9 /tube. WIll add this to the tool box wiht my next order !

Yep, that looks like the stuff. I went to Pegasus and found a nice pic of it and it says it's made from castor oil. Here's a pic for the viewing audience.

[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.

[lovehamr]

kit, I'm glad you did all that crap 'cause I learned a lot. Glad it works now man!