More Stiff Clutch ??

[frankym]

I have been reading lots of posts on the subject and I wanted to redress my stiff clutch once and for all. It takes a huge effort to get this thing to the floor. Here the facts:

Ford 427
BW T-10 close ratio 4spd
Centerforce dual friction clutch - pressure plate 11 inch disc 1+1/8 / 10 spline (installed 1000 miles ago) (the box says it was for a GM, not sure if that matters)
hydraulic clutch master cylinder (likely 3/4 or 7/8 bore, mfg unknown)
aeroquip stainless #4 hose
wildwood pull style slave cylinder (installed 500 miles ago)

The clutch pedal has incredible pressure from the engaged/disengaged positions.

I am trying make a change that gives me a lighter clutch for faster smoother shifting.


I am considering either a hydraulic throwout bearing or buying the push style slave kit from finish line. Not sure if it's a problem with the slave not being strong enough to overcome the resistance from the diaphram spring or whether it is a problem with the throwout bearing configuration. I am inclined to purchase the push style slave as I am very comfortable working with an external setup and very leary of pulling the tranny to replace the throwout bearing with a hydraulic one only to find that I still have a very stiff clutch. I was even kicking around the idea of hooking some kind of hydraulic booster to the clutch master but that sounds way to frankensteinish. Somebody else here mentioned using a Toyota Land Cruiser Push style slave. Any thoughts and suggestions would be appreciated!

fm

[Bob Putnam]

First - Find out exactly how far the clutch pedal must be pushed to get complete disengagement - so that you can get it into reverse without clash.

Then, we'll talk.

[Hotfingrs]

I've used the Centerforce Dual Friction before, and the pedal pressure was at a stock level or less. This was a non hydraulic unit. Lasted many years, and survived weekly trips to the strip. It's predecessor was a Hayes Comp unit, and it didn't last a month.....

[frankym]

Bob,

I won't have access until the weekend to measure but the pedal needs to be ALL the way to the floor to navigate reverse. roughly 5-6 inches from fully engaged to disengaged (floor). The car starts to move after lifting your foot @1-1.5 inches of the floor.

Also, I found that I needed to apply some pressure to the clutch fork using a large pry bar so that I could insert the slave after shorting the length by adjusting the threaded rods to be a total length of "at rest distance" less 1-2 milimeters. Otherwise, it would become extremely difficult to disengage the clutch after the car warmed up to op temp, in fact in first gear with the clutch all the way to the floor, the car used to move/creep, so in order to avoid the partial engage, i effectively moved the starting point of the pull back a hair. The wildwood slave has travel of about 1.38 inches 9per specs). I also used a piece of 1/2 x 1 inch stock to anchor the fixed end of the slave's heimer joint for a firm pulling point on the frame and the slide of the slave is parallel to the frame of the car.

Even still, to race the car and go from 1st to second, the shift is never that fast because it feels like there is resistance or you would need to really shift it hard, it doesn't grind, but it's notchy when doing it fast.

My concern is that the hydraulic throwout versus hydraulic slave alone is not going to ease this clutch. I appreciate your help, thanks,

fm

[jwoodard]

Check the bore size on the master cylinder vs. the slave cylinder. They should be the same size. A mismatch here could be the cause of the stiff feeling clutch.

Jim

[frankym]

the bore on the slave is 7/8 (.88 inches) and the master looks like a girling and is either 3/4 or 7/8 but I don't think the size is the problem because the stroke of the pedal is farely long which is genearlly associated with a smaller master bore; going to a larger bore at the master (relative to the bore at the wheel cylinders or in my case the slave) would give me a shorter stroke and require more pedal effort, since I have good travel and hard pressure, I think the problem would be unrelated to a bore size mismatch, but I am NO expert so I am really not sure.

[frankym]

looks like I have a 3/4 bore girling MC which has a stroke of about 1.4 inches so the stroke is almost identical to the stroke of the slave (1.38) and the bore of the MC is just slightly smaller than the slave (7/8).

[Bob Putnam]

Frankym,

Unfortunately, there's no such thing as a free (clutch) lunch... If you reduce the master cylinder diameter or increase the slave cylinder diameter, you're going to lose throw at the clutch fingers. And probably end up with a problem.

Since this kind of leg pressure is not typical of
a Centerforce clutch, I suspect that there's something binding or creating interference in the clutch or linkage itself - and that's where I'd look first - waay before I started changing hydraulic parts.

[RACER X #99]

Frankym,
Did you buy the matching throwout bearing for thr Centerforce clutch. I have the same clutch and very light pedal. You said you had to insert a large pry bar to install slave??? sounds like you may have a missmatch of parts.

Cranky