hyd clutch pressure

earthman · Apr 18, 2008

Got new 3/4 inch clutch master and 3/4 slave. Exactly what was
used originaly.Problem is that for some reason it takes too much effort to operate now. Would changing cylinder size on either one make operating easier or is it likely that something is defective ?

donsrods · Apr 18, 2008

Since you say it was on there originally, and I assume worked well, one of the two components are probably not ok. Not sure if you should start with the master cylinder or slave.

Is is bled all the way? Do you still have the old parts to start switching them out?

Don

bob w · Apr 18, 2008

Do you have the original clutch fork? Maybe the fork arm from the pivot ball to the place where the slave pushes on it is too short. I have a master/slave/bell housing/fork all from a '60-something Chevy truck and it works like a dream.

earthman · Apr 19, 2008

Thanks for the replies. The system is bled completly and the old parts are gone. The new parts are the same internal diameters as original. Wilwood and CNC from Speedway. Original clutch fork. A longer pedal would be a simple fix but not enough space. Not an engineer so don't know if a larger slave cyl would be easier to push as a larger gear is easier to turn by a smaller one.
Of course then the larger slave piston would not travel as far.

bob w · Apr 19, 2008

You could disconnect the slave cyl from the clutch fork and see how far the pushrod moves as you push the clutch pedal down. You need to figure out how much slave pushrod travel you need to disengage the clutch. If the slave pushrod moves a lot farther than needed, then get a larger dia. slave or a smaller dia master cyl. That way you will get less slave travel for for every inch of clutch pedal travel reducing the force required. The pedal will have to travel farther to do its duty. I guess a simpler question would be, does the clutch engage and disengage in a small amount of pedal movement?
It sounds like the original setup was a custom arrangement, it worked ok for you and nothing has been changed but the two cylinders. If that is true, then disregard everything I wrote. Most people do anyhow (lol). Look for a pinched or obstructed line or a defective cylinder. I'd still try the first step above and see if the hydraulic system works smoothly without actuating the clutch. Usually, pedals have about a 1 to 7 ratio., so if you have a real short pedal arm, extra effort would be expected.

donsrods · Apr 19, 2008

Can you give us some pictures of your pedal, clutch arm, etc? Your pedal should be about 7 times as long in the part from the pivot point up as it is from the pivot point down...........7 to 1 ratio or thereabouts.

Don