Club Cobra - Clutch slave/master question

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Clutch slave/master question

I am working on a CSX1000 (427 Style) Shelby. It uses an (I believe) Afco master cylinder and an original style Girling external slave cylinder. This is a very common setup that Shelby sells and uses on the majority of their cars. It typically takes 5 minutes to to get them completely bled and adjusted. However, on this car we have been having issues with too much free play in the pedal. This isn't what I would call your typical free play. It almost seems like there is too much slop in the master cylinder. We are seeing probably 2-3" of pedal movement before the pedal pushrod acts on the master cylinder piston.

This is the second master cylinder we have put on the car. The first master cylinder did the same thing, so Shelby replaced it under warranty. I had initially thought it was an issue with bleeding all the air, so I took a suggestion and put the slave lower than the master cylinder (then bled it) in hopes that there was an air bubble trapped, but no dice. It is now looking like the master is bad, but I doubt we got two in a row. Maybe we need to bench bleed the master?? I have never had to do that, but I am running out of ideas?

Anybody have any thoughts or experience anything like this?? I am considering calling Afco next.

Thanks! :)

Kris, mine was that way (not 2-3", maybe 3/4"), had to make the adjustment in the pedal box. Mine is probably somewhat different, but not totally different...the rod that pushes the master cylinder (and is connected to the bottom of your pedal with a clevis or ?) was threaded and I just adjusted it away from the pedal to make it effectively longer and take out the slop.

Joe

Just thinking out loud, chin in hand. Is it possible that the master cylinder isn't fully retracting? If the push rod is adjusted too far out to take out play, it could be possible for the stroke of the master to not get far enough back to expose the hole that draws fluid in from the resevoir.

Joe,

I thought of adjusting the pedal in the box, but that would make the pedals be uneven. I am going to triple check to see if any adjustment can be made there

Mike,

I made a custom pushrod. Maybe it is too long?? I'll try to shorten it a bit to see what happens.

Thanks for the ideas guys.

Check the angle of the rod when you press the brake pedal. The clutch and brake pedal have different mounting points where the clevis pins attach. If you have the brake pedal on the clutch the pivot sit's about a 1/4'" too high and it throw's the pivot angle off. I had the same problem with mine.

Rob

Rob,

On the Shelby, the brake and clutch pedals pivot in the same spot. The brakes go to the equilizer bar, while the clutch goes directly to the master cylinder.

I do appreciate the ideas. They all are making me think of solutions, and thats all I can ask for! Thanks :)

Kris:

I believe the diameters are 3/4" for the master and 7/8" for the slave. Is this what you have? Have you bench bled the master before installation?

It may sound over simplified but the fluid displacement ratios have to be correct.

Rick

Rick,

Yes, 3/4" master and a 7/8" slave. I have not bench bled the system, but that is on the agenda for tomorrow. The freeplay in the pedal seems to be the pedal pushrod compressing the return spring in the master, then finally contacting the piston.

Such aggrevation! **)