Hydraulic throw out bearing help

Sooo...  my swap is a 3.5 gm v6 (lx9) in a 2nd gen rx7.

This is a racecar and the clutch needs fully depressed to disengage the clutch ND actually shift gears.  However, it also clamps when the clutch pedal is almost all the way out.

Do I need a bigger bore or smaller bore to get this to react more like a street car?  Meaning disengage further from the fire Wall and engaging further from further out...

My research has confused me.  I was thinking bigger bore is more fluid and that would solve my issue.  Is that correct?  I have a 7/8 bore clutch master.  Do I go to a 1 inch clutch master?  

I'm running a Tilton that I can run a larger one with the same footprint.

Bigger master will run the slave with less pedal travel but more pedal force. Does 1" get you what you need? Does the hydraulic slave have a recommended master size?

For the same travel at the master cylinder, a larger bore will move more fluid and cause more travel at the slave.

It's pedal pressure versus travel versus master diameter:

Larger master = higher pressure and shorter pedal travel.

Smaller master = lower pressure and longer pedal travel.

When I went to a Competition Clutch twin disk setup, they supplied explicit instructions on how to set pedal travel and supplied a modified throwout bearing. Setting it up wrong risks driving the clutch into the flywheel, pressing against the crank thrust bearing, or possibly going over center.

Pull it apart and make sure the disk isn't bent, first.

It is amazing how much runout some aftermarket disks have, either in manufacturing or shipping, and it will cause this behavior.

So, this setup doesn't normally exist in nature.  I fabricobbled it all together.

It's a gm 3.5 engine with like a 1994 Chevy cavalier flywheel, a t56 HTOB, and about 1/4 inch of shims between the htob and the t5 Trans (out of a 2001 camaro v6).

The master is a 7/8 inch tilton.

I have drilled a large hole in the bottom of the bellhousing so I can see what is going on with the clutch when the pedal is pressed.

It just seems that it really wants more fluid to actuate further.  I can always put in a pedal stop, or change the pedal ratio if it ends up being too much fluid movement.

Have the hydraulics been fully and thoroughly bled of all air?   Do you have full stroke travel on the master cylinder-not hitting carpet, mounted correctly to allow full travel, etc.

wawazat said:

Have the hydraulics been fully and thoroughly bled of all air?   Do you have full stroke travel on the master cylinder-not hitting carpet, mounted correctly to allow full travel, etc.

Yes.  I have had these issues for the last 3 years of racing.  Clutch pedal grabs with the clutch very high and requires the pedal to be pushed to the floor to disengage the clutch. 

There are no "problems" with th3 system right now.  I just want to make it better.  I would like the 3ngagement point to be closer to the middle of travel instead of almost at the top.  I would also like the clutch to disengage a little further than all th3 way pushed in.  It makes for slow changes and occasional grinding.

Those are the symptoms of a bent disk.  It does not fully engage until the pressure plate straightens the disk out so it can clamp it down, but it is difficult to shift because the disk drags even with the pressure plate maxed out.  Alternatively you may have a bent finger or two in the pressure plate.

It need not even be assembly error.  I bought a new 4 paddle disk from a reputable source that had one paddle 1/16" off.  Frustrated, I went through a huge stack of old used disks and ended up finding a 215mm disk with no runout.  Clutch disengagement was wonderful after that!

I may sound like a broken record but unless your pedal ratio is really out of whack, 7/8 is already huge for a clutch master, even with an annular slave cylinder.

That would be 2 different pressure plates and 3 different discs...