5 1/2 " clutch problem

[Tony Rolfe]

It looks like there is some serious discussion now on "FC General Discussion" so I will post my question/problem here. I just installed a new 51/2" Tilton clutch on my Carbir Pinto. I can not get the clutch to release or slip.
This is what has been done in replacing the old 71/4" clutch
1. Replaced 3/4" master cylinder with a new 5/8"
2. Replaced Saab slave cylinder with a new Tilton. The piston that came originally with the kit was replaced with one that gave .200" air space between pressure plate fingers and the fully compressed piston.
3. A 38mm throw out bearing is used.
4. Pressure plate, disc etc. are all new
5. When everything was together, the cutch pedal was slowly depressed while trying to find the point where both output flanges could be turned with transmission in gear. (I didn't want to over extend the pressure plate fingers). During this process the cutch never disengaged/slipped.
6. I have around 1-1/4" of mater cylinder push rod travel and 1/4 " of slave cylinder travel. The free play between the slave cylinder and pressure plate is where it should be.
7. The clutch has been bled and re-bled many times starting at the master cylinder back to the slave.
8. The car is plumed in -4 from the master back to the slave cylinder. The Tilton slave cylinder is set up for a -3 fitting unlike the Saab which uses a metric to - 4 fitting. I cut and welded a -3 to a -4 fitting and drilled the hole to the -4 diameter. There are no leaks. Could this cause my slave cylinder piston travel to be affected?
I have had the transaxle, flywheel and clutch apart many times. Any thoughts or suggestions?

[Steve Davis]

1)... Have you tested the flywheel/pressure plate/clutch assembly to verify that the clutch disc CAN BE RELEASED? (disc too thick?.. maybe)
2). Have you verified the amount of throw required to release the disc? With a .200 air gap and only .250 slave cylinder movement ... is .050 enough to release the disc?

Steve, FV80

[David Ferguson]

Any chance your -4 fitting into the slave cylinder is too long, and is either - locking the piston from moving (like a set screw), or blocking the flow of fluid. Can you verify the piston moves with the pedal?

[BorkRacing]

Can you verify the piston moves with the pedal?

Look thru the timing mark opening if you have one and look at what point the slave touches the clutch.

Also sometimes the first time you try to release the clutch it seems to stick, I have had to use a lot of force to break it free.

[Bobsy SR 6]

Tony

i just went through similar problems with my clutch. In speaking with Tilton tech I was informed that a 5/8” master will produce .360” (approx) travel at the annular bearing for 1” of master cylinder travel. Most pressure plates require .250” of travel to disengage. So your free play may be too much. I ended up at .120” of free play but my issue ended up being a bent disc causing drag and no release. Tilton tech reps are very helpful and knowledgeable so a few calls to them my be very helpful.

Best
Tom

[Tony Rolfe]

Thank you to everyone who responded to my question concerning the 51/2" Tilton clutch. Still no solution so I have decided to go back to the old tried and true 7 1/4" clutch. I guess that couple of extra pounds of rotating mass probably means I won't be FC national champion (again).

[Rick Silver]

Is the step the correct size on your flywheel? When you install the clutch cover and pressure plate do the teeth deflect in the correct way and the correct distance?

What spring forces on the clutch cover plate - is it gray, orange?

Are you certain of your engine flange surface to the clutch fingers distance?

Which Tilton hydraulic release housing are you using? Is the bleed hole in the correct 12 o'clock position?

[scotty82]

What color spring does the clutch have . If it is a Grey spring the release load is 850 pounds. This will not only be hard to depress if you are at 3 to 1 pedal ratio.. but it will destroy the thrust side on the main bearings
I set up all my customers with WHITE spring .. this is 150 Lb-Ft torque with a release load of around 470/480

[DaveW]

I ran a 5.5" clutch on my FC (Pinto) for years. There is no mechanical reason why it should not work if set up correctly. So, did you ever determine the issue with the 5.5" setup?

[DaveW]

...5. When everything was together, the cutch pedal was slowly depressed while trying to find the point where both output flanges could be turned with transmission in gear. (I didn't want to over extend the pressure plate fingers). During this process the cutch never disengaged/slipped.
6. I have around 1-1/4" of mater cylinder push rod travel and 1/4 " of slave cylinder travel. The free play between the slave cylinder and pressure plate is where it should be....Any thoughts or suggestions?

Is the Tilton fluid (pressure) area larger than the SAAB? Barring anything obvious, it sounds like with the 5/8 master, you're not getting enough fluid displacement to move the slave piston far enough to disengage. Did you ever try it with the 3/4 master? Did you ever try it with less initial clearance (0.1" vs 0.2")?

SAAB slave pressure area below:

[Rick Silver]

Is the Tilton fluid (pressure) area larger than the SAAB? Barring anything obvious, it sounds like with the 5/8 master, you're not getting enough fluid displacement to move the slave piston far enough to disengage. Did you ever try it with the 3/4 master? Did you ever try it with less initial clearance (0.1" vs 0.2")?

Agree with everything Dave said. I just converted my OEM Van Diemen slave to a Tilton. I used the ULP 1.44 inch hydraulic set up and it worked exactly as it was supposed to. I used a 0.190 " clearance and I kept my previous 0.75 in master even though they recommended a 5/8. The 3/4 works fine. I set up my pedal stop just like the instructions, about 0.200 inches at the slave further than when it just starts to disengage. I did have to add about 0.20 more inches of travel to my pedal.

[Tony Rolfe]

I have run out of time so I put the trusty 71/4" back in. I think Dave's idea about fluid displacement is the source of the problem. The new 5 1/2 " clutch will be next winter's project (again). Thank you for everyone's help.